Cailin - what you're saying made sense in the 19th century. I'm not sure it's still the case today.
Men don't need to procreate, for a start. Actually, it was probably only ever a need for the upper classes anyway, monarchs and the such, to have somebody to inherit the family's property, political functions, land, or continue the business, etc. For the poor, progeny was another mouth to feed. Sure, they might also look after you in your old age, but still, children were more of a liability (not to mention the consequence of limited contraceptive options) than a necessity.
I'm not sure there's all that much in it for men these days, to be honest. Yes, 80% of housework and childcare is still done by the women - but the bulk of that housework and childcare didn't exist, in the first place, if it wasn't for family life.
I think in general it's mostly women who strive for children and therefore need the emotional and financial safety of raising them in a family, if possible, rather than alone. That's why, on the whole, women are more keen to marry. It's a safety net for mothers, first and foremost.
That's also why they put up with doing 80% of the work. The biology element has little to do with men doing far less childcare, imho. After all, biology only matters during pregnancy and breastfeeding, which is a relatively short period in the grand scheme of raising a child to adulthood. I think the real reason is that if more women insisted on a more equal division of household chores, then even fewer men would agree to have a family in the first place. Negotiating power isn't on the woman's side when her biological clock is ticking and the bloke can take or leave marriage and kids.