A couple of years ago no one was accepting bitcoin as a payment and now one can buy a lot of things with bitcoin. I believe that those who accept bitcoin as a payment should also accept bitusd as a payment. In the end of the day the merchant doesn't want to have bitcoin's volatility but rather bitusd stability.

The reason that not many merchants accept bitusd...yet..is that bitshares in reality is only starting now..It can't be compared with bitcoin's network effect..yet..I think that once POS for bitassets are in place (thank you @kencode) and with some more marketing and effort from everyone from the bitshares community, bitassets can become very popular.