When I was in the uk the main times for going out for meals with others were work do's, Xmas etc. And always split 50 / 50 as it was a rarity.
On holiday it was the same.
I remember one awful meal out with someone with a calculator who was outraged at the suggestion of splitting the bill because she hadn't had a pudding. Completely spoilt the evening.
Living here we tend to eat out in groups much more often and have noticed that almost everyone tends to pay for what they've had, I guess you have to as its more frequent and none of us know how long our savings are going to last.
I confess I do keep track in my head of what we've had to make sure we get charged the right amount as have been overcharged on many occasions and always scrutinise the bill for the same reason.