The "having more mental space" argument is very interesting to me. There's some interesting science around this across a number of disciplines. The most readable intro is probably this one but the idea goes deep: if the organism has to devote cycles to survival, there are less cycles to devote to longer-term projects. This shakes out everywhere, including mating strategies.

So I think it's plausible, at least. But I'm trying to guard against telling myself a story that I want to hear.