Why do they need to?
For Sony, they don't need to, as it's outselling the 360 is Europe by massive amounts, and in the US by a reasonable amount.
For Gamers, why should they? Sure everything would be nicer, cheaper, but the PS3 even at the current price represents a massive bargain, you are getting more bang for buck than any other consumer device around.
I can understand why Microsoft are price cutting, desperation. However you only have to look at the last European 360 price cut (about 3 months back), which only provided a 2 week upwards blip in the otherwise sliding 360 sales.