That's a good point (and I think I've also seen a very strong gender bias in taxi drivers, a little less strong in Lyft drivers, and weakest in bus drivers), but also, I think this sort of thing applies pretty firmly to relatively low-wage jobs. Certainly these aren't minimum-wage, but they're also not, like, mid-six-figures. (I think! Given the risks I'd be happy to know that these jobs do actually get to mid-six-figure wages.)

I suspect that white-collar senior management jobs contribute a lot more than pizza delivery jobs to the fact that men make more money than women in total. (But probably this is also true for median or first-decile wage?)