>Sure, but you could have a single account called "bills."
Ah, I specifically don't because:
1) Capital One gives you 25 savings accounts, but only 3 checking accounts, and
2) There's a federal limit of 6 withdrawals per month from savings accounts, and
3) I already use my 3 allotted checking accounts for unpredictable day-to-day purchases (an account for my spending budget, an account for my wife's spending budget, and a shared account for family/house expenses like groceries/gas).
I sometimes bundle together some things like subscriptions so 2-3 expenses can pull from the same account sometimes, but there are the occasional problems where a service or product will charge more than once per month (unexpectedly) and I don't want to risk exceeding 6 withdrawals/month and getting an account shut down. Seems easier to just separate everything out so you don't have to think/worry about it.
And separate accounts remind me of what the funds in each are for (and seeing each one filled is reassuring to know that there was enough money to transfer into each envelope without any issues -- if you see a 0 in an account early in the month, you have time to figure out how to pay for that thing, instead of getting surprised when it comes due and a shared account can't cover it). That seems useful enough -- seems like no downsides and nothing but improvements over having a single account that mixes everything.
I'd probably do things the same way even if CO offered 25 checking accounts, although it might make sense to consolidate a few of the smaller recurring expenses into slightly fewer, more high-level accounts to make things easier at-a-glance.