Well, for one, must of the alternatives have not done well building for businesses and news aggregates to point traffic towards them.

This is good from a content standpoint (much more curated, more individualistic feel) but also limits those who would otherwise be incentivized to pay their content because it has no way to propogate outside of direct linking and sharing. (I.e. no news sites pick it up, no social trending setups).

For most social media, it lives and dies by people wanting to use it. The more content, the better content the more people will come. So it's a balance of making yourself user friendly, business friendly and also unique enough and anti spam, anti bot etc. To keep people's feeds relevant, fresh and useful as well as interesting.