Well, yes, first of all because I never liked flashes. Mostly because I started with a bridge camera probably, and the flash was totally useless like in any compact camera.
Then, well, weird, but a flash IMO draws more attention than a tripod... and I always have the tripod in my car.
Then well, I know in some cases, to kill some shadows, a flash is a must, but we come to point #2: I don't like to have to learn new stuff, and I know you need to practice quite a bit to really use a proper flash. plugging it in and just shooting won't work. I don't like to feel like a total noob againn, and most important, I have no time to practice lately.
Ah yes, also: to use a 580EX with the 18-55?! LOL, comon! And with a tele lense, not sure it would be any use
I know the 580 is not that cheap, but well, if I'll buy one, I want the best one if possible
We'll see. I am not really conviced I'll use it that much, but I'll probably end up buying it anyway one day... and hopefully its price would have dropped a bit by then