Quite simply, it's all about money. People will sell whatever is in demand.
Japanese food, for example, is a curiosity among many non-Japanese in N. America, with a relatively low number of people knowing quality Japanese cuisine. Restaurants take advantage of this often and will claim to sell such cuisine to draw in business. Sometimes, all they'll do is add something like sushi to their menu, or in other cases, they'll make a poor rendition of an actual dish. Sadly, most people don't seem to know the difference, and will frequent a place, thinking they're getting something authentic.

I remember a friend inviting me to some mock-Japanese restaurant before. Quite an amusing experience. He was hyped about it, but the food wasn't all that great. The rice wasn't even the right type, nor was it even cooked right. I mean, c'mon, at the very least, get the rice right!