Well, Steemit is a social media platform. The purpose of Steemit is interpersonal communications, and it's rival cryptocurrencies are focused on various other things, none of which are drivers of traffic to the degree that social media is.
Settlements, contracts, stores of value, payment mechanisms, and the other purposes for which these currencies are made, do not drive traffic even remotely to the degree which social media does.
It is hugely surprising to me that Steemit is not first on the list, tbqh.
Thanks!