A) Assumes anyone single ceases to exist when not working. It's absolutely insane to think "no gf, must be no hobby of course." It's more likely one's hobbies just haven't led to a romantic partnership.
B) Is possibly the millineal version of gen x's "gym" and boomers' "grocery store," women often say they don't want to be asked out there either.
C) Then the advice isn't "get a hobby," it's pray your friends set you up with anyone.