Because on one level, we are all just competing for finite resources - especially quality females - economics is in that context an ordinal competition, not cardinal.[1] But on another level, it's the mutual cooperation, wealth creation from nothing (making the "finite" a little less finite and a little more infinite), etc that allows us to advance both as a society and as individuals.
[1]There is an interesting tie into Mises here if I wanted to rabbit hole it (value is subjective, not measurable in cardinal units, and exists only in the mind as a ranked preference of options)