Why do we think that is? I can tell you first hand, albeit with a little bias. It is because today's teams/scouts want one thing from a pitcher: velocity. If you aren't approaching 94-95, you don't really get much of a look, unless you won a bunch of games for a major college team. So young pitchers are throwing every pitch with max effort to get max velocity/spin. And arms go kaboom. So teams need to be really careful with their expensive assets.
Forgive the personal story, but it illustrates my point. My son was a 6'4", 240 lb righty pitcher, in college from 2011-2015, division II. Topped out at 89-90 on the gun, with an arm slot that made his 2-seamer move in on righty hitters like a frisbee on good days. Decent but not great slider, pretty good change. Never threw with max effort - it negated his movement. Never had a ton of success on his college team, the metal bats did not help a pitcher like him either. His game was inducing weak contact, and the metal negated some of his effectiveness. 3 straight summers he played in the Ohio Collegiate wood bat league, and just dominated. Broke a ton of bat handles with the 2-seamer at 89. After one 9 inning 3-hit shutout, the umpire asked him who drafted him, and my son just shrugged. I told him, if it ain't 95, they ain't interested. The ump said "that's how it is now. It used to be about just getting guys out."
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