Addressing the modern development of player usage. Players are being built today for maximum performance but durability and longevity are taking a backseat.
Pitching is the obvious place we notice this. Starters are throwing harder than ever for 80 or 100 pitches tops then leaving the game. Complete game wins today are rare. Pitching into the 8th is rare.
Players are hitting the weight room at maximum effort to launch 400' shots. They aren't taking whatever body they developed at their off season job and using spring training to get in shape. It's become a year round effort.