According to RunSignup's RaceTrends report 54% of all race participants are women. Yet, according to the same report, only a measly 3% of races offer female-specific shirt sizes.
There's obviously a good reason why race directors choose to offer unisex shirts instead (which are mostly male-fit shirts): convenience. When you're struggling to pin down shirt sizes to order, ordering a whole different set of shirts on top in their own sizes and fit can complicate things a bit.
That said, many women runners often resent receiving unisex shirts and end up rarely wearing them, if ever. So if you want to make your female participants feel valued and appreciated, you should try and be in the minority of events and include female-specific sizes for your finisher shirts.