There's a lot of variables.
Married, I kind of agree with treating it as family/shared money, because that's the (lifetime) commitment there, even if it often doesn't actually work out that way in practice.
Earlier, pre-kids relationships: could be 50/50, could be by proportional earnings, kind of depends how you see the relationship going/lasting.
Later life relationships, it gets complicated: do you have kids, does he, how much time do each set of kids spend with you both, how is the split of "family" responsibilities for children, housework, mental load etc?
I think both parties' contributions to the relationship should be equal, but that isn't necessarily the same thing as equal financial contributions, and it depends a lot on the individual situation.