I had wondered that once too. But I looked at pictures of lactating apes and the amount of breast hair did vary from none, to a bit hairy- but possibly long hair that overhangs the breasts? Hard to tell from photos.
However, Patty's again to me looks like carpet/fur covered breasts. I know gorillas have hair, but theirs is carpet-thick/fur-like to me as opposed to obvious hair of chimps or orangutans that have areas of thinning . But the gorilla mothers have barer breasts, again trying to discern from I-net photos and a controversial bf photo.