Two biggest factors in the changes in pitcher usage (IMO of course). - hitters are better and especially bigger Seaver et al regularly faced 165 lb middle infielders and other 'bat control' types or defensive specialists, who, for the most part, they KNEW couldn't hurt them so, unless a base hit was going to beat you there, it was easy to switch to pitch-to-contact mode while saving bullets for later. Today we see 215 lb middle IFs who can take a hurler out of the park to the oppo field so in-game 'resting' is less of an option. - pitchers are better also! this has the effect of narrowing the talent gap between your top starters and the guys in the pen. So when your childhood starters, certainly the top three anyway, were facing a lineup the 3rd or 4th time around it's likely that, even somewhat fatigued, they were still a better bet in the 7th or 8th innings than all but maybe your ace reliever. The result is starters in the game longer to pick up more decisions thanks in part to lower pitch counts containing fewer max-out ABs. If teams could find more guys who could pitch you a 'Maddux' (CG w/< 100 pitches) then, great. Good luck with that.