Sure, but that's the only system we know is stable even over the hundred years or so we've been doing the experiment.
I would be cautiously in favour of STV, but PR systems seem to get rid of the 'you can vote the bastards out' feature in favour of permanent government by the same people in various coalitions.
Being able to change the government without violence is, I think, the only real argument in favour of representative democracy, and it's an important feature, because it's what stops democracies having periodic civil wars, and focuses the parties on at least trying to appear to represent the median voter.
err, no?