Roland Perry writes:

In message , at 22:43:53 on Mon, 5 Mar 2012,
Phil remarked:
Only supermarkets/convinience stores offer cashback, as it reduces the
amount of cash they need to, pay to, bank. This is only on debit cards,
probably all sorts of consumer credit rules about giving cash on a
credit card.

The problem with giving cash-back on a credit card is that the
cardholder is charged a different rate of interest on cash advances,
and often a fee (and even a zero interest-free period). As a customer,
you wouldn't want that 'penalty' applying to whole of your
transaction, goods as well as cash.

Amex Cards are treated as a credit card by retailers, due mostly to
what it costs them, even though they are, usually, charge cards.

Many of them are credit cards now.
True, but I would never have one personally. So few places accept them,
they can seriously limit your choice of places to eat when away on
business.