Why can't the parks promote themselves, surely theyre the best channels for promotion? Eg offer backstage tours, a backstage insight video, and treat all their fans equal rather than just those holding the biggest power online.
Let's pretend your argument here was about promoting an independent movie you have made. The argument you are essentially putting across is why shouldn't I release and promote the movie through my own website, rather than putting it on Netflix. The answer is pretty obvious.
The same translates across to this, TPWW have a large audience, so it is very easy for companies to promote themselves, to a receptive audience. I would not call it shilling out at all, as by putting content on channels like TPPW, their content has potential to have a much higher reach, to a much bigger number of people, than offering something physical. It would simply be impractical to do some of the things YouTube enable in reality. You are not going to get 100,000 people around a backstage tour of a park, in a week. Probably struggle to do that in 6 months to a year. You can 'virtually' do that through YouTube in less than a day if your audience is large enough. The same goes for all their other promotional stuff. It can reach a huge amount of people, very quickly. Yes, it will never be the same as actually being there, but when done right, it is good entertainment to watch.
This way of marketing is not unique, it is a massive way many companies do stuff now through YouTube with huge amounts of YouTubers doing in in what ever their channel is about. It is a very good way to get stuff to people who might not even know they like that sort of stuff, to get into it and interested in it. People who would have never in a million years, paid for a backstage tour for example.
So in short, yes they do deserve it, because from what they have created themselves, they have to ability to reach a very large audience, very quickly.