I like this site, shows how even 'simple' things can get complicated, in many cases you can see the logic that got them there.

The Canadian Decathlon one is here (go to the filter) - https://www.decathlon.ca/en/c/22252/sports - and you can see the train of thought that it makes sense to put a filter in as sportswear comes in male/female. Those filters probably make a bit more sense when filtering a specific category too but I can see how that would all get in without someone considering how absurd it'd look when filtering all products.