1) Some women react positively to catcalling. Even if one in a hundred, then it would be enough, because the cost is low. As an analogy, receiving spam is also annoying, but a tiny fraction of humans react by sending their money, which rewards the spammers.
Note that the catcallers only need to believe that it’s worthwhile; it needn’t actually be.
Note that the catcallers only need to believe that it’s worthwhile; it needn’t actually be.