Given that it's almost always women disappointed about having boys, are fathers-to-be allowed to weep over the prospect of a daughter? Or would people give them short shrift for it?
Which people? Society in general would applaud them -. see China, see India, see the example of Henry VIII. It is considered normal and expected for men to want a copy of themselves and to acquire it by exploiting women.
Here on mumsnet, men might be given short shrift for wanting sons, because let's face it, the women here are very aware that carrying a pregnancy for nine months and then going through birth is very different from, you know, just using someone else's body to try and make a copy of yourself.
Stop trying to equate very different things. Reality matters.
If a woman is foolish enough to go through 5 pregnancies in order to have a daughter, then it is her body that's harmed by it, and the boys have still a chance to be loved by their father.
If a man in patriarchy forces a woman to go through pregnancy after pregnancy so he can have a son, then HE does not suffer for his foolishness, the woman does, and the daughters haven't much chance to be loved by their mother, either, when she knows there's another forced pregnancy coming after giving birth to a girl.