I do dislike meanness of any sort, but the ladies I dine out with regularly always recognise the designated driver doesn't drink, and goes out of her way to pick us up and drop us off after a night out. We pay for our own meals splitting the cost of a bottle of wine or other alcoholic drinks between the drinkers. We also, between us, buy the soft drinks for whoever drives. It seems the fairest way. One friend always has a liqueur coffee after her meal and doesn't expect it to be added to the total. It can get messy if you don't have a fair system for paying on group night outs.
OH is very generous and if we take friends staying with us out for a meal he insists on paying. Sadly, we have some old friends, one couple, who never, ever reciprocate, even though they have good incomes and a wealthy lifestyle. Last time we stayed with them we went out to a lovely restaurant and at the end of the meal he made it fairly clear OH would pay half of the cost. I was mortified but the 'friend' didn't flinch and neither did his wife. OH and I had a good old chin-wag about it afterwards but he says he won't change. Most of our friends are equally as generous, which is lovely. (I might not be so hasty in inviting that particular couple to stay again, perhaps.)