I've definitely never tipped when I've used the service.
Yes, but you can afford it, or you wouldn't be using the service
I wouldn't say that people having their groceries deliver "can afford it" - as rutabega's already pointed out, the delivery fee is less than a bus ride, and some people don't have a car, so it's not a matter of buying a luxury, it's a matter of needing groceries. It's not always practical or economical to do several little shops a week....
With Tesco you have the option to have your groceries delivered green, without bags so I appreciate that he comes into the kitchen and unpacks the crates and takes them with him. I don't need the plastic bags, I don't need the crates and I don't have to carry individual items from the door to the kitchen.
I think I'd still rather unpack myself and give the bags back (I know that's an option with Ocado) - maybe it's just me, but I wouldn't be comfortable standing there watching while someone unpacks my groceries - as it is I feel guilty when the driver has to make multiple trips from the van to my door. Maybe the "pack it yourself" mentality has taken over for me....