One really important point is that normal people don't want to use volatile currencies. Bitcoin and other cryptocurrencies have been really volatile which has scared a lot of people away.

Steem is in really unique position with Steem dollar (price stable cryptocurrency). That has been tried earlier, but there hasn't been any easy way for common people to get any stablecoins. But now they do, they just have to blog. This combination can boost Steem's network effect quite well.