I live in a country where this service is not available (anywhere!) But imagine being an elderly or person with disabilities, and this is the only job you can do. Imagine looking forward to contributing with what you can, and then someone like you shows up and takes over their tasks, just because they are not fast enough for you to not wait a few more minutes in line.

In any case, it should be the store to blame, because they don’t open more cash registers or hire more people and let customers in line