Steemit is very new as I understand it so the size of the user base at this point doesn't matter much compared to the trajectory it is taking.

I think its inaccurate to compare Steemit to Bitcoin as the purpose and utility of the two are so far apart in terms of usecases and incentives. Why would someone open a Bitcoin wallet? If they understand what a technical breakthrough it represents and they are interested in it or want to invest. Other than that its if they want to use Bitcoin for something, but even now Bitcoin is at an early stage in adoption. It's not normal to be able to spend your Bitcoin anywhere you walk into and it's not normal to be able to walk into a shop, bank or currency exchange and buy some like you would a normal currency. There may be a lot of acceptance and it may be increasing, but you can't go to the supermarket and rely on being able to pay with Bitcoins yet.

Don't get me wrong, I still think Bitcoin has a lot of potential uses in the world, large scale remittances across borders, proof of existence, a replacement for the SSL trust system, but aside from investing in it why would an average person hold a Bitcoin wallet today? There is no added benefit for day to day payments over using a debit card or Apple pay. Bitcoin's user base is people that understand it well enough to see what is going to happen with it (a very small fraction of the population), not the average person out to buy stuff on the street today. If there is no incentive for the average person to own a Bitcoin wallet, they won't.

If we compare that to someone posting on Reddit or Twitter every day, at the moment they get to communicate to others and there the benefit ends. Along comes Steemit where people are making posts that regularly make actual money for them. Your comment (not even a full post, a comment) currently stands at $40 because some people found it interesting. Just by making your comment you could buy yourself a new pair of jeans or a meal out. So now we should look at these two cases:

1. What is the benefit of posting on Reddit over Steemit (momentum since you already have an account, maybe exposure reaching more people since its a larger site)
2. What is the benefit of posting on Steemit over Reddit (rewards worth actual money, with a chance that if you make an effort to create an interesting post or something a lot of people find valuable, you could be rewarded with quite a lot of money)

There is no barrier to entry with Steemit unlike Bitcoin, you don't have to spend money and time buying Bitcoins or Steem to give it a try, and there is potentially huge benefit to posting there over Reddit or any other social media site. Even if the rewards are sparse, people pay for scratch cards and lottery tickets where they have a tiny chance of winning even a few thousand dollars. If you make zero effort with your post and just upload pictures of your dinner each day to Steem there is still the chance one of your posts could become popular and you could make thousands off it.

It is early days and one sticking point is how the average person can convert their Steem into USD but I can't imagine that at some point the main media won't pick up on the story of people making simple but popular posts and being rewarded to the tune of thousands of dollars by them and when that happens we may see adoption spike to put it lightly.

This is my opinion and it is quite possible that I may have made assumptions here that may not bear out, but it seems logical to me and likely to pan out like this. If anyone has any thoughts about pitfalls I'm not seeing though then I would be interested to hear them (both from an academic perspective and also because maybe Steem might want to consider what they can do about them).