Cab drivers and their cell phones

I was in a cab a few days ago on my way home from work when it struck me--why are cab drivers ALWAYS talking on their phones? Who do they talk to all the time? I take cabs quite often (twice a week when I was commuting from Houston and the past few days I've taken one home from the office every day) and the cab driver is always talking on the phone (in some foreign language) for the entire cab ride back to Brooklyn. It doesn't matter what time it is--11 am, 2 am, 4 pm, they're always on the phone. Do they talk to other cab drivers? Do they talk to their friends and family? Do they have enough friends and family to constantly be on the phone with? I'm perplexed.