just thought of a good reason: I speak English and know a little of German, French, Spanish. Now I'm imagining speaking a slavic language or Greek and trying to navigate this site. If the site were in one of the three languages where I can use a dictionary, I bet I'd get a lot of tags wrong.
you are right. there are so many inaccurate tags, completely off-topic tags - I don't get it. if someone's going to the trouble to post, why not label accurately? but they call me the grammar Nazi at work LOL, and I'm in technical work