Living together right now, so our finances are separate. We go 50/50 on rent but don't keep track of bills, grocery, entertainment expenditures, etc. but I would guess that's split pretty much down the middle, too. Higher earner probably pays a bit more, but I'm just guessing. My partner prefers to cover all the car expenses (I don't drive but do receive the benefit of car rides on the rare occasions when I can't take transit, when we drive places, or when visiting out-of-town friends/family.)
If we eventually commit to a family and a lifetime together by marrying, I would expect we'd make it one big pot. Children and career sacrifices for the good of the family are going to come along, and it would only make sense that we'd present a united front should illness, job loss, or downturns in our respective industries come along. In my mind, that's one of the defining differences between marriage and less-official unions like common-law or cohabitation; the family as one unit.
Lots of couples have a yours/mine/ours system, which I think is great if that's what works in their situation. Sometimes it's just easier, avoids arguments, or makes it possible to save and invest according to a plan. And it doesn't have to mean you're not all-in. If your spouse gets sick and can't work, will your income cover the rent, groceries, and shoes for the kids, or will you keep a spreadsheet and issue an IOU for his/her half? You might have a veneer of separate-ness, but if, in the end, the money in the separate accounts is going to go towards things for the family or funding retirement for you as a couple, you are operating as one unit. You're just organizing things a certain way that works for your situation.