The whole tipping thing is very difficult for those of us from backgrounds  where tipping isn't customary...It is quite difficult to get your head around  what situations require what response, if you haven't grown up with it.  I have visited your shores  3 times now, and  each time am  quite unsure....The desire is to do the right thing, but sometimes it isn't immediately clear what that is...  Often it is easy enough.

EDIT to add.....  It wouldn't occur to me to tip a flight attendant or baggage handler.... I am still very doubtful how appropriate that is