Thats because its not the 90's anymore
Cash is no longer king. Finance is.
Why sell you a £17k car for example, for £15.5k cash, when they can hang on till someone comes along with a PX that they can make a profit on, pays roughly the asking price (so they make a profit on the car), takes out the balance on finance through them ( so the finance company pays them a commision) and then has all the add on's like GAP insurance and uses them for services etc etc
A £17k sticker price actually means, if the right customer buys it, it will make them £19k+.
Therefore, someone offering them £15.5k CASH is no longer an attractive proposition