because it was non profitable after the crash, and 9/11 people wernt willing to pay out $10,000 per round trip. sadly. and with air travel in a slump it just got worse.
airbus refused then to supply parts after Air-France pulled out of the project, so that was it.
It was non-profitable before the crash. I think the french took the decision to ground it after the crash in order to cut its loss's, the last French Concord finished 31st May. British Airways did'nt immediately suspend its flights until about 5 months afterwards as they (quite rightly) saw the accident as just an accident and not necessarily a design flaw (clearly something needed improving but didnt warrent a total no-fly policy).
The lining of fuel tanks with bullet-proof Kevlar, a reinforced undercarriage etc really didnt change the French's idea of the plane and its more commited to Airbus Industries now so it was never really going to come back as they prefer to put their money in more profitable aircraft (which I suppose is fair)

I posted some other news that the BBC have put together over
here