DH and I have separate finances... entirely separate, now that I think of it. I don't think we've currently got even a bill in both our names! I don't think we ever really thought about it one way or the other, it just slipped our minds to ever get any joint accounts or anything. Obviously we've got the same billing address, but beyond that, I don't think there's anything!
The house we are selling is in my name, because DH already owned a house when we met, and then we moved to a new area not too very long after. We were renting out the first house when we bought the current one, and we weren't yet married, so it was just easier that way.
We are buying our new house together in both of our names, though. I don't know if we'll get joint bills once that's all settled - whatever ends up being easiest, I'm sure.
We certainly never intended it to be that way, and neither of us has mindfully kept separate for financial protection or anything like that. We trust each other implicitly, it's just worked out fine for us is all, and nobody has ever questioned it. It's never made anything difficult in any way.