My theory is that there are behaviors which build alliances within one sex to the detriment of individual relationships with the other sex.

I have no strong opinion about whether this contributes to individual reproductive chances, though I can make up some theories about why it might.

People don't just need to produce babies, they need to support themselves and their children-- alliances within one's own gender can quite useful. It's also conceivable that intra gender alliances are good tools for limiting the mating opportunities of low-status competitors of one's own gender.

A female example might be women who spend a lot of time commiserating with each other about how awful men in general and their husbands in particular are. This is not to deny that sometimes men are a problem for women, but putting a strong availability bias on their negative traits can push somewhat bad situations towards worse.

For both sexes, a fair amount of work is put into convincing low status members of one's own sex to not even try to attract someone. I don't know how much this is in play in societies where people aren't as expected to get their own mates.

It's also conceivable that catcalling is a spandrel-- it's a side effect of homophobia, with men trying to prove to other men (who can be quite dangerous) that they are attracted to women. Doing something low-cost to prove that one is attracted to women is easier than than doing something which might actually attract women.