Steem has the exact same problem that Bitcoin did back in the day, it's so new and uncertain it needs to get small scale adoption and to hold value before they'll even consider adapting it to steam.

For what it's worth, I've signed up with coinpayments and on my site have many altcoin options available for when my game releases including Steem, since I'd be totally happy if people just dumped their altcoins on me and have more to gain if I get attention for altcoin adoption.