infielddad,
You bring up good points about how we do not know what is discussed between players and coaches.
A good example would be Ray Tanner, who routinely has many more walk ons that one might consider desirable, however, my understanding is that he gets lots of kids and parents calling especially from alumni, offers them walk on opportunities but players and their folks know it's most likely a long shot. You might find this very prevelant among schools where generations of families attended the school, the player has no intention of going anywhere else, but only wants a chance to try out. If the coach is upfront in his intentions, no problem. Years ago the coach could give books, or small scholarships, and the kids would be happy to sit the bench, he can't do that anymore, but why not give them a chance to try out? The NCAA allows all teams to hold open tryouts, and no fall roster limit, perhaps still a lot for that reason.
I know that Polk did this, and very upset that now he had to turn players away who normally might have a chance to just practice with the team. You might find this is one of the reasons why SEC rosters are so large, lots of these schools include generations of familes that intended, and for many families, there is no where else you will go, but where your mama, papa, sisters, brothers, uncles, aunts and grandma and grandpa went. Not all coaches subscribe to that philosophy, regardless of alumni families.
I don't know if it is like that on the west coast.