It's exactly the emphasis on velocity. For one thing, we've developed a bunch of throwers, not pitchers. Throwers think they have to go 100% on every pitch. The aces of yesteryear could throw hard when they needed to, but they knew that 85% would get the job done most of the time. They had the extra gear when they needed it. Old timers knew how to pitch, how to set hitters up. They called their own game and always had since they were kids. Can you imagine Bob Gibson being told the pitches would be called from the bench?