There've been kidnappings.
Also in Japan where women are opting out of relationships/ having children, men in large numbers have opted out of society entirely.
In the end most men expect a woman and rather than looking at the things that they can't find one- sex selective abortion, the restrictive role imposed on mothers. They do other things.
I don't think those men would want to be pregnant. They want a woman to look after them/ home/ and for sex as well.