It bothers me too, but I figure 1) it's television, so they have to go with what's popular, 2) it's television, so they have to go with what's cheaper, and 3) some of these things have become so standard that if you want something else, you might just as well invent a new universe.

Hence... Firefly! :-D

Err, not really, but... really, ST has its own world that is clearly American. If we want something else, we should really be looking at other sci-fi or perhaps inventing our own.