Why did the Banks family have a Black butler on the Fresh Prince of Bel Air, shouldn't he have been Mexican?

Ultimately, because the writer(s) decided on it, of course. Otherwise, it may have been an attempt to portray a family that based their hiring decisions on merit rather than on ethnicity or gender. More cynically, one might follow the money, and suspect the show's producers of calculating better odds for the target audience approving of the character based on racial characteristics. To my knowledge, there is actually no such thing as a female butler, but that may have changed in recent times.

The obvious answer is that The Fresh Prince was a Black show, the butler was an actor, not actually a butler, and the producers were supporting Black actors.

If we're pretending the show is real, it's because they were Black too, they probably wanted to have a butler that they felt at home with, that felt like one of the family.

I think you were trying to make a racist joke. Not a well thought out one though. If this question had been flipped around, it'd get reported.

The butler was not mowing gardens. I only recall butlers making food and attending the family, not mowing grass and such.

Aw come on it was a show you are the only person in the world that care about dumb things like that and make it a race thing

huh? mexican is a nationality not a race dumbass they can be white,black,asian
and if i do have a maid is going to be black cause there pieces of **** worthless
hispanics at least they have some class and culture and respect people

Now girlll i know ya aint hatin on ma boi G!