To all you indignant faffers:
I am not the rude arse sighing, moaning or tooting behind you. Unlike some, I have manners.
Whilst you dither and time waste, I am thinking ahead to what I'm going to do next, be it buy my paper as quickly as possible, determine the most succinct way of ordering my drinks to avoid confusion, or overtake you at the next opportunity without you noticing until it's too late for you to put your hoof down to try and stop me (why do slow drivers do that?).
I find that those people who need extra time (doddery old ladies who can't handle their change too easily, for example) are often the most apologetic about the delay. Because they don't live in their own little selfish bubble. Treating such people with impatience is churlish and unacceptable.
It is also highly inefficient, as impatience only makes things worse. I have found such encounters to be the perfect opportunity to show some consideration, and offer to help, or at the least, smile and make some remark about there being no need to panic, I'm happy to wait for them.
Because I was brought up to think about other people, y'see?