@Lee

I use self-service because:

a) There is usually one free so I know I won't be queuing behind some arse that doesn't think to look for purse\wallet until asked for payment and then remembers they've got 37 different vouchers they want to use

b) you get a plastic bag to put things in without having to ask

c) I fancy the bird at my local Tesco who has the job of pressing the "he looks over 18" button whenever I run some Merlot through the system .... which is often