Because players never come back from injuries and play at a high level again, nope.
David Wright? A complete bum still, isn't even batting .400
Johan Santana? That no-hitter shouldn't have counted.
Jake Peavy? He's just lucky I suppose.
Josh Hamilton? Probably won't even break Bonds' record.
These are just players off the top of my head from this season alone. They all still suck coming back from injuries. I'm sure you can find more evidence by looking more thoroughly at this and other seasons.