I spend a lot of time in the States and what is clear and unambiguous to my US friends is anything but to me.

There are all kinds of unwritten rules about tipping. I once left a handbag containing some very valuable jewellery in a restaurant. As soon as I realised I phoned and they agreed to hold it. I was some distance away and couldn't get back until early the next day. They agreed to meet me before their opening time and handed over my bag, after asking some security questions to establish I was the owner.

I was so grateful I tried to reward the manager. She was quite offended by that.

I told this story to several US pals who said they wouldn't have tried to tip. How does it make sense to tip someone for 'just' doing a certain job, yet not when someone goes above and beyond to help me out?

It's also not clear which jobs should be tipped and which aren't. I'm sure if you grew up in the US it's all second nature and you probably can't understand why we don't follow your system. But to a frequent visitor the unwritten rules on tipping are inconsistent and confusing.