I only use self checkout in a pinch, in large part as an act of Luddism. Self checkouts take away entry level work. I have a choice to support the workers, so I take it. Not to mention how awful the interfaces are when you're buying fresh veg -- I find that it's usually faster to wait for an available checker. In a lot of grocery stores near me, I do my own bagging and some even have a second conveyer for that purpose.
If you want to support the workers and actually make a difference in someone’s life, get someone to take your bags to your car and tip that person. They get to take a break and walk outside, and make some extra cash under the table.
I don’t think opting-out of self checkout counts as “supporting the workers”.
The more that people use self checkout, the fewer employees the store can get away with. Opting out slows the process of automating jobs away.
As for my car... most often I'm either by transit or walking. Anyway, I could be wrong but I don't think stores offer help out where I live. I've never heard it in the decade that I've lived here.
