Because most of the time, there is no need for replay. The one or two times a game there is a need for it, though, it should be available. Plus, umpires do more than just call balls/strikes and safe/out. Come on, you can do better that. And wouldn't it be nice to be able to correct a blown call? I sure think so. Hell, I bet the umps think so, too. I know Jim Joyce would've been a lot happier last year.