Cannot wait my turn at the store. My grocery store has self check out lanes, where you scan and a belt takes your items to a bagging area. Normal procedure is to scan items, then pay, and then bag. I had purchased 2 large bags of cat and dog food so I had filled the bagging area up and was not able to utilize the divider they provide so the next person can ring out. I'm bagging as fast as I can so I could place the divider in between my purchases and hers. Note I also had cupcakes at the furthest point from my position, making them vulnerable to be squashed if she where to start her purchase. So instead of waiting she sends her 2 extra large laundry detergents down the belt and they start crushing my cupcakes! I saw so much red I had to keep my mouth shut or risk being thrown into to deepest darkest ring of ehell. I was able to grab both her bottles and set them aside before the cupcakes got damaged, I finished bagging and and walked out.
I have to say, it drives me crazy when someone fills up the bagging area at the self-checkout and then makes me wait to start scanning my groceries. I think it's a bit SS to assume that an entire line of people should wait while you finish getting your things together. If it looks like I might be holding the line up, I will move my groceries over to the side so that the person behind me can start scanning. The woman should have noticed your cupcakes, but you also probably should have moved your cupcakes so that she could start on her own groceries.
My grocery store has some of those self-checkout lanes (which I love) but they do not
have "divider bars" (?) in the bagging area. So my procedure when I use those lanes is to scan, bag, and then pay. (Otherwise it is inevitable that someone else will start to scan in and send down their groceries, despite the fact that there is no way
to physically separate out different orders in the bagging area.)
To me it feels a bit SS if it drives you crazy to have to wait for the customer in front of you to finish their transaction before you start yours. (And yes, bagging your groceries is part of the whole transaction.)