I think (if it is not a disorder) attention span can be trained. It takes discipline and a true interest into a topic other than just a vague excitement. If you are able to state what topics you are interested in for yourself, you might be able to concentrate on 10-30 Minutes of the same topic. People who are really into The Kardashians are able to watch a whole 50 Minute episode of them. So it is not the problem of concentration for them, it is more that they need something put in front of them for that they can feel a passion or enthusiasm they deeply care about - even it is just The Kardashians. Here is the thing: People have no problem browsing 2h+ of tiktok, but can not concentrate on 10x 20min video? I think if you have a real interest in something you can get through longer videos. Do you look for thing you really care about or do you actively looking for a distraction when you browse tiktok? It is not a bad thing to use it that way. After a long day of work, it can relax your brain browsing real shallow, short clips. But daily, in high doses… then I think it is maybe another reason people do it (escapism, etc.)