Lots of photographers need different lenses for their particular use. None of the Canon lenses are horrible, they may have weakneses, but nothing and noone is perfect.
Some of the best photographers are doing very well with Canon lenses, and some even pull down seven figure earnings.
If a lens doesn't seem to be what I want, I'm not going to worry about someone who wants it, because they probably have a good reason. I happen to have a Canon 28mm f/2.8, and for the price I paid, its pretty good. I bought it for $25.00, but even for the normal used price of $200 its a excellent lens. I've had lots worse.
Both of these were taken wide open at f/2.8.