It because where they look. If you look for fish in a desert, you'll have problems finding them. If you go to the sea, then you might find plenty. Of course you still would need to use the "right bait".

The men who think that sex is scarce, do so because they want sex with specific women who simply might not like them.

But if you simply want sex, you can "use a net". And go to places where people go looking for sex. Chances are that if they were more open about who to have sex with, they find someone. But they want the "hot 20 something" that has 10-20 years less than them. Not the average divorced woman with slight overweight.

The expression "boys would be boys" (we don't use it in spanish XD) is meant to excuse certain behaviours by men. But not all people agree with that expression and for some people have become synonym with "I know is wrong but I want a pass". XD