Everything has changed in the past 15 years or so. It's a trickle-down effect. Major-league teams are expecting bigger athletes, so the colleges are, too. High school kids are lifting year-round. Nutrition is better.
High schools have trainers.
There's so much more going on now. Baseball players shunned weights 30 years ago. Now, even high school players pump iron year-round in elaborate school weight rooms. But I think the most important thing is flexibility. Flexibility enhances power, and more flexible players are less susceptible to injury.