In fall ball there are 35+ players competing for roster spots and playing time in the spring. With the exception of maybe a handful of delusional walk ons everyone is capable of earning playing time. But it’s a numbers game and not everyone can.
There’s also a pecking order of opportunity. I’ve seen some players get more of an opportunity to stick than others. One of my son’s travel teammates was hailed by his college coach as one of his top recruits ever. He was handed his position three straight years and lost it by the beginning of conference play each season.
Players start out doing the best they can. Given not all opportunity is equal they have to stay physically and mentally prepared to take advantage of every opportunity. There are cases of players thinking they’re giving 100% and they’re not. That’s their fault. But there are cases of players who are and the numbers just don’t work out.
One of the biggest mistakes I saw in college ball selection was players selecting their dream school who noticed them versus other programs that had much greater interest.
Note: I was the one who brought the 50% transfer number to this board and another board about ten years ago. It was in an NCAA article on baseball.