phalenopsis there's no need to be so passive aggressive - I'm just playing devil's advocate. FWIW I am a feminist, and quite pleased that a lot of the outdated wedding concepts have been abandoned.
I'm just curious because where there is a disagreement, someone has to compromise. You seem to think it should always be the b&g, whereas I don't see why that automatically has to be the case.
If there aren't enough spaces for the guests that everyone wants, someone has to lose out. You could equally say that the parents were being selfish for wanting their friends at the exclusion of some of the bride and groom's, couldn't you?
Another way of looking at is to say that if the parent can't accept that they don't get to dictate things, they don't have to pay. No one is forcing them to give their child money, presumably they do it because they love their children and want them to be happy and have a good day. Maybe that would also include letting their children choose who they want to attend. Or maybe not, clearly.
I am still uncomfortable with the concept that contributing means you get to prioritise what you want over what they want, unless you've said so up front. The OP hasn't even suggested this.