Create a place where people can pay for steem with a debit card in house.
I think this has a lot more legal barriers to consider. And it also makes the purchasing of STEEM possible off of existing exchanges, which could complicate price discovery, especially when the holder of that STEEM in question gained it at the outset of the blockchain's creation - when there was no price at all.
In other words, it would be messy all around. But I'm pretty sure it doesn't happen because of the legal aspects. I could be wrong though.