My daughter is a D1 P4 slapper. There has definitely been a decline in slappers in college. I would say they number one reason is the change in the, "out of the box", rule. Before slappers just needed to have any part of their foot touching the line in the box even if most of the foot was out. Now the entire foot needs to be on or inside the line. I have no idea why NCAA changed that rule, I hate seeing such a dynamic part of the game being taken away. People will say,"learn better fundamentals", but the problem is in travel and high school it's still being played with the old rules, this causes problems with the freshman when they move up, especially when the opposing team gets tape on the player and sees her tendencies. Coaches will tell the ump before the game to watch said player and then proceed to pitch outside to draw the player out.