I guess it boils down to biology. There is very much a built-in system to our bodies hardwired to make us care about our own offspring; and it does its job well. Trying to enforce “objective, logical benefit” onto how people behave as parents is unfortunately an uphill task. It’d be similar if you were to try to oppose an open park in a city because “Logically, it serves no functional purpose since people can take their walks on the sidewalk.”