Is it that you are either free for all or you can limit to your own sex or a sex of your choice? So could men say they only want woman? What about trans people.
Do we start adding in religion, political affiliation, race, etc etc etc.
Woman not feeling safe with unknown (and largely unvetted) Male drivers (or passengers) is a valid concern. It feels more like a bandaid than an actual fix, but it is an "Easy" solution to a problem. The ideal should be that we don't need this, not that we add in more filters like this. But for many reasons we as a society are not there.