well, there's still xposed modules and such that do the same thing, I'm not sure if they'd be detected.
It's a step. Anyone who knows how to root may very well be able to disable the check.
At the very least, it keeps the opportunists from cheating.
I have been blocked from Pokémon GO since last September because they blocked rooted phones. I have yet to find a way to get around this regular rootcloak doesn't work and it does detect Xposed modules which I need for my phone to function so I can't remove those.
@Niantic: Now that you've blocked GPS spoofing... Unblock rooted devices please? :'(