To clarify - I was talking about "spending money". Our allowances are mostly spent via credit card, but when I categorize the expense it goes in as "DH Allowance" or "DW Allowance".
We do exactly as you do, and the rule is that neither one gets to opine on how the other spends their monthly allowance.
OK, so we are talking about the same thing.
I find that doing this has two benefits.
First, it lessens any potential conflict. There have been times that we haven't had the spending money category. But, then I spend way more on certain categories than DH does (books for example). And, he spends more than me on other categories. For example, just this year he spend spent several hundred dollars on a house designing program. If this came out of budgeted money for software for us collectively I would have been upset (he says he will never move, he just got the software for fun). But, since it came out of his spending money, I see that money as already having been "spent" since it is in his category so I don't care how he spends it. It has no effect on me whether he spends it on that software or on books or at Starbucks.
Second, it provides a vehicle to control certain discretionary spending. Unlike some people here, we could easily spend way more money than we can safely spend. I have lots of things I could spend money on and have expensive tastes. Now, I can
happily spend much less than that but I do need to watch what I spend.
One of things we put in spending money is computers. DH and I both like high end computers and can spend a lot of money on them. By having that come out of spending money, I know that each month I need to set aside some of the spending money for future computer replacements (currently I have $3500 set aside from saved up spending money which I will spend on a new computer in about a year and may buy a new iPad next year as well).
So, by setting a spending money category that is high enough to cover the cost of a new computer every few years I make sure that I don't overspend on it since things like my books also come out of the same category.