Even though I'm fairly new (almost 2 months) cashiers don't have to treat every time like it's my first week. If you leave me alone, I'll bag for you. If not, I'll leave and do something else.
I leave baggers alone unless they're slow or wasting time talking instead of bagging. I always thank them after a big order or partularly fussy customer.
I always get thanked for bagging. If I'm doing really terrible then a bagger from another lane will come over and be like "you can go now" but not in a really rude way, just in a way that I'll know I was sucking hard, haha.