Why does Sore Wait a Day?

Jock bought this up when I was in Baton Rouge and I am experiencing it first hand presently. How come when you do some kinda strenuous exercise the next day you are fine but the day after you feel like your muscles are on fire? I lifted and lowered weights in the Jim Friday. Yesterday I was fine and today I can barely move? What the hell is Sore saving it for? Go ahead and get it over with.