Even the front page of Steemit encourages people to sign up to get paid, so as you pointed out there's certainly a monetary aspect to the whole thing and to a lot of the activity. An argument could be made for building a platform that's not tied to any one particular cryptocurrency, so that way you could introduce new currencies and switch them around based on what's doing well in the market.

As for the future of DTube, if you take a look at https://new.d.tube you'll get a hint at what they're working on. Basically, the new Dtube, in addition to earning Steem, is going to have its own token and currency, and have better integration with YouTube, so you can upload a video to YouTube and then embed it into a DTube post, basically. If I'm understanding correctly, in the new DTube videos will always be able to earn DTube Tokens for as long as they're on the website, so even if someone finds a video you did a while ago and upvotes it, it can still earn more tokens.