Why phone now?!

It seems theres a new trend. A customer will queue up, waiting patiently. And then when it gets to there turn they whip out they're phone and start talking to someone, leaving me standing there waiting for their order. I'm not psychic and the customers seem completely oblivious to the fact that there are people waiting behind them.

I just talk over they're conversation and so they still get served quickly. But I don't understand how they can think its ok to just start phoning someone when you're about to be served (especially when you're holding up a queue). Why can't they wait a few seconds until they've ordered and paid and then phone they're friend to bitch about some bitch?