How appalling if you are pregnant. Common courtesy would be fora man to at least help with bags.
I dont ever tip sainsburys drivers but if I get a friendly one, I chat and say thanks very much. I do my job without a lot of thanks, shouldnt everyone?
I tip waiters, any service person who has done a particularly good service, I often let people "keep the change" but I have a family to keep, a budget to keep and several charities and 2 sponsor kids to support.
You do what feels right. If its not within your bduget or means, then dont guility give. Defeats the purpose hey!