A lot of people. "He's a high draft pick, he's got great scouting reports, he's young for this level and so on."
Now some of that has value, even at higher levels, but only in context of actual performance.
I'm not writing Crawford off because he's young enough to turn it around, heck, maybe Walding at 24 has turned it around (though I won't believe it until he repeats it in Lehigh). But at this point he needs to show progress, and he's better off in AAA until he figures out a swing that will make him a decent hitter.
Once a player gets to A ball, I want to see performance (rookie leagues are getting your feet wet). Moniak is young for Lakewood, but I'd like him better if he was hitting .300 with a .370 OBP, he'll grow into power, but the contact and plate discipline should be there now.
Tocci has improved, he's hitting well in AA, just don't expect even average gap power from him, but his walk rate has risen so he may be able to put up a decent OBP at the top of the order. He's an example why being young matters, not because it made him a better prospect per se, but because it gave him time to develop into a better prospect, he could have flatlined just as easily.
Conversely if an older player is slugging it out in AAA over an extended period (i.e. they've seen him enough to adjust) he's worth a look, it may be he's just taking advantage of lower velocity FBs, but it also may mean he's made adjustments and figured out how to hit (that's why you pay scouts, to verify the stasticis, it's not enough to use numbers, you need to investigate the causality behind the numbers).