I think that there are several reasons why Steemit has less subscribers than other social media, despite the economic incentive.
The first one maybe precisely the motto that the platform has used to promote itself. It is allegedly a site where you get paid for posting, voting, and commenting on other people’s posts. Well, we all know it is not that simple. When people realize how much extra work and time is involved in that “being paid for posting and commenting”, then the hype goes down and the word is spread. You may call it false advertisement.
Derived from this economic aspect is the issue of security. Lots of complicated security measures to keep in mind because your account can be hacked and there’s no way to help you recover what you lose. Most people do not want to have to bother with that.
The display Steemit has may also be less attractive for youth who are used to facebook, youtube or instagram. The immediacy of the info and the interactivity may also play against it.
Steemit has quite a few norms or regulations that keep many people away from it. Also, the power disparity among the different hierarchies of users may contradict the idea of the decentralized/democratized network some people bring to the platform. When it comes to making money on line most people want simple task, even if repetitive. They don’t want to deal with some social etiquette or lobbying that will eventually, very slowly sometimes, get you to a position where you can start to make some money.
Some people say that the lack of advertisement may also be discoursing users. I don’t see it like that, but people get attracted by the most unusual things, so who knows.
Finally, the instability of the crypto market is something that definitely has kept some people away from Steemit. Lots of work and time without of a guarantee. That is probably the most important factor. The other, more popular social media offer just fun and gossiping. I guess most people would rather pay for that, than being paid for what we all do.