My understanding is that corks create very varying seals in wine bottles, which means that the amount of oxygen that can get in is very variable. Hence the bottle-to-bottle variability we are used to in fine wine. (Supposedly the variation in the neck of the bottle is also sometimes to blame.)
Random oxidation as a wine defect is not talked about much, but in my experience it's at least as high a % as TCA, if not rather higher. I love it when wineries I work with switch to screwcaps because each bottle tastes the same. I like my wine artisanal, not the packaging.