the same reason why you have a name, think you are a troll, claim a nationality, etc. none of that shit matters. Everything is relative, but in human society people don't get over actions associated with language. That's why language has it's power because of the full history of what it represents.
600 yrs ago people didn't really use terms like black and white like we do, but ever since those terms started to be used for some race/economic shit, alot of bad, good, beautiful, and horrendous things have happened, so in the minds of millions shit aint as simple as physics anymore....