Scouting is all about tools and size for position players. Scouting has a harder time with Heart, Passion, and a players ability to grind.
I think some Bonus Babies do not feel a need to Grind and display Passion. Others like Trout and Harper have shown that they have the make up to play hard everyday.
If you are not a top round pick the money is not there to be able to even afford to play the game in the minors without family support.