First thing that popped into my head (rightfully or wrongly) is the 'accustomed to a lifestyle' theory, that maybe their routines and successes on other platforms simply don't translate and they lose interest before they can adjust.
I think a lot of folks (I can't speak for everyone, but definitely myself) enjoyed this platform initially because it was more based on interaction and building relationships. I can't confirm this, but from what I've seen, most other social media platforms seem a lot more algorhythmic and calculated. You can make the right moves (content, keywords, ad placements, etc.) and never have to say a word to anyone directly. Steemit isn't like that; you almost have to be a part of the community to succeed here. There aren't any shortcuts or formulas; you just have to meet people and be active. I've noticed in my personal experience here that just posting isn't even enough sometimes. I'd venture to say I've gained more friendly relationships by interacting on other peoples' content than sharing my own.
In my opinion, as many parallels as they may have, Steemit (+DTube) and Youtube are two hugely different animals. I think a Redditor might have an easier time here than a Youtuber, and as much as I love DTube, I just don't think it's quite developed enough to be able to hold an individual up on that alone. I think the Redditor would at least be more accustomed to the frequent posting, commenting, browsing, etc. It seems the people who are successful on DTube do a lot more than just post videos. It's about jumping around between the different platforms and communities in a way that will cumulatively add up to a relative level of success.
It's what we love about it for the people that are here, but I think it can also be the part that drives others away who are used to the usual Youtube, Facebook, Instagram image of success.
Not that it would need to be on there, but if we were to ever write a "Guide for Youtubian Migration" this would be extremely important.
The probably get used to a specific strategy. Not that I know it, but for example.
I'm being a little silly, just woke up, need caffeine, but you are on to something there.
Dude! Yes I totally agree, I think you articulated and made some important key points much better than I (I was on the opposite end, too late at night, caffeine was wearing off lol).
Having that standard of authenticity is super valuable here.
And just throwing it out there (now that I'm back to my PC and not on mobile), if you ever DO write that guide and want another set of hands, I'm all for it!