It's simple evolution. We're biological beings, and so we probably are instinctively attracted to a partner who's likely to have as many healthy offspring as possible. If you want to be part of the cause behind why no modern society has enough children anymore, then that's your choice, but your kind will not be represented in future generations. https://medium.com/non-violence/stakeholder-control-compensating-parents-for-their-sacrifices-to-prevent-extinction-of-258bd3d8f3aa