I've definitely noticed a different response from waitstaff when I'm on my own than when I'm out with friends; it seems as though, in the former case, a waiter

I've definitely noticed a different response from waitstaff when I'm on my own than when I'm out with friends; it seems as though, in the former case, a waiter will tend to be a bit less formal and more friendly than otherwise. It's a little odd, perhaps, but it also tends to result in better service, so I'm not about to complain.