I used to work as a grocery store bagger and it honestly depended. I always said “yes” when somebody asked because I was more than happy to let somebody else do my job, but there were definitely instances in which they bagged things so badly that I had to take over and correct them. Believe it or not, there is a tried and true “method” for bagging (both paper and plastic) and there were some things people did that made it borderline dangerous for their health or just impractical. Think: putting cleaning chemicals with the meat, or putting heavy stuff on top of the bread.

I definitely also much preferred people asking compared to people walking over and just pushing me aside, which they did many times.

If you don’t trust yourself to bag things “right” so that you don’t end up with a mess in your car when you get home, then just let somebody who’s trained do it for you. If you do trust yourself to do it, then at least ask politely.

This is crazy, I’m in the UK and we have to do it ourselves, I didn’t even realise it was a thing that people packed your bags for you just buying your food. For me that feels like a service you should tip for.

I mean, I’m in New Jersey. We don’t get plastic bags anymore, and most places don’t offer paper bags, so it’s kind of mandatory to bring your own bags or buy reusable bags from the store. But you are definitely bagging your own shit.
Edit: I used to cashier and bag when I was in high school anyway, so I’m still fast with it.

It may depend on the store. My local publix trains it’s employees like Chick-fil-A does, and they probably would be offended if you didn’t let them help you.

The baggers at my local food lion (if there is a single one in the store) are offended that they have to help you at all (probably because they’re expecting you to be the fifth person today to come back in the store demanding a refund for the one cracked egg in their dozen)