I am social democrat, and as such I am for all people to have living wages.. (and I am actually proponent of basic income and progressive taxes)

However, checkout assistants are not very well paid and the job is horrible (it's not the worst, arguably, but could be improved).

I do not however feel responsible for the bad moral decisions of other people. My action in itself doesn't increase profits of the wealthy, it's actions of other people. These people need to be made socially responsible (for example via progressive taxation), not me.

There was a time when you got good money to work in a grocery store, even in a checkout. I have (older) family members who decided not to finish college because they were making so much money at the grocery store, with pensions, in positions that would only pay minimum wage nowadays.