What does your wife do if she gets pregnant? Parental allowance might possibly not be an option then? Does she go back to work quickly? I've met quite a few women who always talked big about wanting to return to work quickly, but then suddenly after the birth wanted to spend more time with the little treasure or the child was so complicated that external care wasn't possible.
Self-employed people also receive parental allowance. I agree with you, though, that some ladies were surprised by how much they actually got attached to the little one or simply realized that 3 months might be too early or too short. But these were all women who were employed and thus only needed a short note to turn 3 months into 12 (the employer just has to swallow it). That might look quite different for a managing partner...
Nice that apparently this is always the problem of the mothers...
Given the described income situations, it would probably be wise to reverse the default case, yes. At least from a rational point of view; for the little ones there are other factors involved as well (see above).
But children are simply born by women. That’s how it is. Neither law, society, nor medicine changes that. The belly is there, the restrictions, the need for care. Before and after the birth. It can only be partially switched off or transferred to others.