It's simply what I've seen over the years - used to love it. Then I started finding issues with the stuff, and after I had an empty eject in pieces, causing damage to my glasses, I went to Winchester. They buried the problem and refused to help. I also had an issue with a primer from them, same story. The higher end Winchester ammo tends to be good, though. The Remington 115gr JHP bargain ammo is actually quite good for both target AND carry - even Evan Marshall of Stopping Power fame said it had a good track record.
I also avoind the steel cased Russian import pistol ammo, even though the issues I saw are PROBABLY fixed by now...Wolf 9mm ammo used to shoot sparks out the barrel, and occasional ejected empties would be trailing sparks. I think they were using rifle/pistol powder blends at the time.