The sizing issue definitely comes up, especially when one size is different in different stores and some people wear different shoe sizes in shoes, boots, trainers etc.
I never try anything on (the only times were for my partner's sake), I know what will look good on me and what I will make look good or else

I also tend to buy shoes/accessories that will go with lots of different clothes so I barely ever have to buy specific ones.
I will say though that I always leave things tidy and pick up stuff or put things in the right places in stores (and the library), I have respect for the shop staff!