I dont' think there is a wrong reason for taking home shelter kitties. unless you intent to stick them in your cooking box or something similar.
I also dunno why people say that black cats are overlooked as they're always the first to go at barks usually, it's unusual/damaged looking cats that tend to be left.
We don't have a preference on what our cats look like, but have ended up with tabbies due to their ability to get on with a cat we already have rather choosing them for their looks. There are cats we would love to have but can't because they were unsuitable or already taken.