I think it all boils down to common courtesy, which, unfortunately, is not all that common anymore. Sometimes people do have valid reasons for taking so long to write checks or put their stuff away. Many times, as I've observed, you just have a person who doesn't give a rat's a@# about the people behind them. I've actually witnessed someone get grippy about the person in front of them taking too long, then they get up to the cashier and take forever themselves. Seems people want YOU to hurry along so they can hold every one else up themselves. What kind of ego does THAT take??
So, Anna, having worked in retail quite a while, I can tell you, sometimes it's the people who are ahead and sometimes the ones behind who are the problem. When a person is at the cashier with a bunch of people wating behind them, they shouldn't dig into the depths of their purse for 2 minutes counting out the EXACT change when they could have given the cashier another bill and accepted the change in a MUCH shorted amount of time. Also, the person behind, instead of standing there chatting with your buddy in line, fuming while the person ahead takes forever ONLY to not pull out your loyalty card/ form of payment until AFTER the cashier is done ringing you up, well that's inconsiderate, too.
Bottom line is, consider the other people in line just as important, or, better yet MORE important than you. When I go through a line, no one has to ask me for my bonus card. I have it out. I NEVER write checks, but, when I did, I was working on it while the cashier was ringing me up. If we all thought of others instead of ourselves in the grocery store, things would go more smoothly and faster.
Don't EVEN get me started about USCAN. 98% of all the problems at USCAN are operator error and most of those are because the customer can't be bothered to pay attention to what they are doing.