My best friend is a night owl, doesn't have a girlfriend, and lives in California, so I do tend to talk to him after 10 pm (my time) a lot. It can be a necessity, especially when I'm on above-ground subway platforms and it's after 11 pm. If I'm talking on the phone, that means that someone knows I'm alive and there's also a slimmer chance that I'll be attacked. (At least this is what I believe. Please do not disabuse me of this notion.)

I do try and call people back if/when they call when I'm in line for a cashier or a teller. But I'll also talk on the phone on the bus to my boyfriend's because I try not to answer the phone when I'm at his place.