I also think that the times had something to do with it. Back in the "old days," especially in an italian family, I believe that it was some kind of an ego thing for the men to have as many boys as possible.
BINGO!!
Mike, despite his attempts to act American (like marrying Miss All-American Yankee Kay Adams) proved he was true Old-World Italian. He may have loved his children equally but he held out high hopes for his son.... not his daughter (Mike tries to talk Anthony into staying in school and becoming a lawyer. The only advice he gives to Mary is to stop making gnocchi with her cousin
).
Mike was a lot like his father. The only time we (nearly) see Vito blow his cool is when he was assuring the safe return home (from Sicily) of his son. The only time we see Mike "lose it" is when he learns a son of his was "killed" (not even Vito did THAT).
