I was just (rhetorically) asked by a lecturer
You don't really prefer YouTube over lectures, do you?
The plain and simple answer is: Yes. I do like watching lectures on YouTube more than attending them. Let me elaborate on this.
Side note: When I write YouTube in the following, I'm not limiting the statements on this particular platform. I mean any professional video streaming website. A very good alternative is Vimeo, for example.
Reasons for providing online lectures
Lectures are typically only offered every second semester. For me, most interesting lectures are in the winter semester. This means I have a lot of overlapping lectures. And never forget that there are some days when you're ill.
If a lecture is on YouTube, you can simply watch it whenever you have time.
Rate of Words
People speak very slow. You are able to listen to at least double the speed in which they are able to talk. Even faster, if they need to write at the same time.
On YouTube, you can play any video in double speed. Just try it yourself:
For 15 lectures of 1.5 hours each, this means I waste over 11 hours.
For some lectures, the lecturer is much too loud for me. It is hard to focus on new concepts if you're thinking about just going to the back of the room.
At the same time, some lecturers could speak up a bit.
This really depends on where you sit. Of course, depending on the lecturer, the room and your ears you could choose your seat. However, you usually also need to see the blackboard. So in case your eyes are not so good either, this might not be so easy.
On YouTube, you just turn the volume up or down to your personal preference.
Rate of Progress per day
Although people speak slow, some lecturers make progress very fast. For some statements, you need time to think about it. Although I could hear the statement much faster, after it was said I need a pause to process it.
It is impossible to get those pauses right if more than a single student is in the room. Everybody has different previous knowledge. And even if two students had exactly the same lectures before, one might have an easier time understanding a new concept than another.
On YouTube, you can simply pause the video. In lectures, you have to repeat it afterwards or simply ignore the fact that you didn't completely understand it.
Rate of Progress per semester
If I'm really interested in something, I can spend a lot of time with that topic. It doesn't feel natural to me to stop, just because 1.5 hours are over.
Lectures are about three months, then you have an exam. For most students and lectures, that's it. They will never come back to most things they've learned. However, sometimes you need something you know you had in a lecture. If it was a lecture which is available on YouTube, you can simply search for it.
In case the lecture has a good book or you have lecture notes, this might also work with "live lectures". However, usually people tend to say things in a very different way than how they would write it. Sometimes it just happens that you know that you understood a concept, but you need a refresher on it. This might work much faster if it is available via YouTube.
Lectures are typically in lecture rooms. A lot of people are there. Some are playing on their smartphones, some come late, others bounce their legs. The other students are just distracting. They are not necessary at this point.
Also, there are internal distractions: I might be hungry or sleepy. I can't just take a 5 minute nap in the lecture. I also feel like I shouldn't just eat in the lecture as it might distract fellow students.
It is not possible to get everything always right. Lecturers will sometimes say things in a wrong way or in a way which is misleading. If the lectures are split up into small pieces, they can re-make the part which was wrong. Or at least put a text overlay there to mention the mistake. As many students over the years will listen to the lectures, it seems to be more likely that errors will be spotted and noted.
It is not really possible to make a lecture interactive. Yes, there are good options like socrative where you can allow students to simply post an answer anonymously. But compare that to multiple choice in YouTube videos where students can thinks as long as they want about a problem. Or even free answers, where you allow the student to check for themselves if they got it right, wrong or if they need a clarification.
I really don't like questions in lectures. Either they are too easy and I am bugged by that or wondering if I got something really wrong. Or they are too hard and I would need more than the usual 5 seconds to think about the question. Or I just was thinking about something else and I need some more context to understand the question / answer in the expected way.
What would I do with a YouTube video if I just lost the context? I would skip back a minute.
Most German universities are heavily funded by the public. There is no good reason to not make the content created by tax payers available to all tax payers.
Reasons against providing online lectures
Creating an online lecture is time intensive. The video has to be made, cut and uploaded. In case of errors, they should be fixed. Ideally, the video should be cut into small sections or at least an index should be created (see Videos of Prof. Henze, for example. Every lecture has a lot of links to parts within the video to make the content more accessible)
So time / money is a valid reason why lectures are not available online.
Pseudo-reasons against online lectures
Lecture halls would be empty
So what? If we really don't need them (which I really doubt), we could use them for something else. For example, for paper discussion groups such as the one I organized for machine learning (see ML-KA/PDG). Or we could have more small rooms for learning in silence / in groups.
This is plain wrong. A professional video portal always has a comment section. So it is possible to have a discussion.
Ideally, online lectures would be hosted on a platform which is suitable for lectures. This means it should have a Q&A part directly linked to lectures where students can ask questions and answer them. Quite similar to StackOverflow. I think I have seen that on coursera. Sebastian Thrun said students answered the questions of other students so fast, that he only watched the questions and answers popping up. Only in rare cases he had to answer questions or correct a wrong answer.
Students don't get to know each other
People don't get to know each other in lecture halls. Most try to have at least one empty seat between themselves and students they don't know. If there are waiting times, at least half of the students look at their smartphones.
Students get to know each other in leisure time activities, Facebook groups for the different lectures, in search of other students for exam preparation (via e-mail lists and Facebook groups) or via student groups like my machine learning group ML-KA.