In our situation its got nothing to do with trust why we don't have joint accounts. We were together for 4 years before we got married..what worked for us with bills, worked for us..so we didn't change it. We've now been together for almost 13 years and keeping it separate still works. I do better with money when it's on a debit card..he prefers cash. I know exactly what's being spent b/c I'm the only one swiping on the account. We honestly never really argue or fight..but when we do money is never one of those things.
Same for us. Our 16th anniversary is coming up feb 28th, and trust is not even an issue. Ease and convenience are. Well, that and I would be annoyed if I had to call her and ask if I had enough money to put gas in my truck. I trust her implicitly, and she sees all the statements, and knows that we haven't been late on a bill payment in many years.