An interesting question and, since I have no children, one that I can't answer directly.
However, I do suspect the answer to this question today would be different from 39 years ago, when the young wife and I got married. We were 23 and 25, respectively, and each of us had, to a rough approximation, zero assets. We just opened a joint bank account and went forward with life together; we didn't know that anyone else did it differently and didn't think much about it. Over the subsequent years, I sometimes heard work colleagues talk offhandedly about his accounts and her accounts, and who paid which bills. That always seemed odd to me.
However, as I look around today, I see people marrying much later than the young wife and I did. They often both have established careers and more substantial assets by the time they marry. Also, it seems that they almost universally live together prior to marriage (we did not). Under those circumstances, I can see that having established separate accounting while living together but not yet married, couples might just continue the practice after the marriage.
Just another reminder, I suppose, that all roads lead to Rome.