Earlier quoted context omitted.
YouTube has been such a big boon to the world in helping people learn. The amount of people who have learnt several skills from YouTube enabling them to make a living is very very large. I know several people who had non STEM education and taught them CS via YouTube and went on to have good SWE careers. Whole of MIT OCS is hosted on Youtube. All of Khan Academy videos are also hosted on Youtube.
They could be hosted elsewhere. Why should free education material that is already funded by donations be locked behind ad based hosting? Hosting is not that expensive if you're using only those services. Especially in the countries where it's mostly being used.
That is why almost nobody bothers to do it themselves outside of big tech.