Mostly because it’s a meme, a.k.a. dumb humor. Memes generally don’t require intricate thought. And they are frequently on the level of “haha, funny coincidence”.

Like, yeah, some people will read it the way that you did, but it’s not like anyone will get convinced of skin color segregation from this meme. And while I don’t exactly find the thought pleasant of some greasy racist feeling reassured by this shitty meme, it doesn’t take the “haha, funny coincidence” away from me.