Your argument with TR aside - consider this.
How is a player to know WHY he received no calls from colleges? Any player who automatically assumes no calls means he can't play anywhere is never going to play anywhere.
A showcase does two things for them. First, it gives then a chance to compare themselves to players outside their own conference. They may very well stink it up at the showcase, but they will have learned something essential, and that is that their talent is not at the level they once believed it to be. In that way the showcase would have been valuable to them.
Second, it gives coaches whom would otherwise never know who they are a chance to see them. Believe it or not, it actually is possible that a player is not right for 100 coaches and yet there is one who would consider that player a perfect fit for his present needs and syle of coaching. This is the type of player who needs the showcase the most.
Being proactive may not always get you what you want. But NOT being proactive gets you no where.