Bear in mind these are peak velocities on fastballs. More typical or "cruising" speeds will run lower.
You do see kids who are sometimes worn out at the end of fall and overdue for their off-season shut down, so folks can say they had an off day or whatever. But this is at least some objective indication of where kids really throw.
It also shows how few of the very high MPH guys are really out there -- though I do think this varies year to year, and I know a few years back we had a run of 90+ guys in the Richmond area alone.