The hard-sell warranties are the problem
Went into one of the newly merged Curry's/PC World out of town shops the other day. It was to buy a TV that I knew was a good price and a good spec ... I could hardly believe it myself.
The staff on the floor were actually helpful and polite. However, when I got to pay, the guy behind the till went straight into the hard sell on the like-for-like replacement cover and then got mightily offended when I politely refused.
Until they remove the incentives that lead to that behaviour, they'll continue to alienate their customers.