Confuses me even if you add the apostrophe ;)

Carson sends in this photo:

While stopping at a restroom in southern New Mexico, near Socorro, we saw this abuse. We had a Sharpie and thought about fixing the sign.

Can anyone tell me what “Dogs’ Restrooms” would even be? A roll of plastic poo bags?
Or is this sign simply advertising a stop where dogs are present and restrooms are available?