Why does it seem like pitchers in the minors or even, say, coming out of college, are generally tagged as being starters or relievers early in their pro career? This happens and then the starter gets 6-ish innings of experience 5 day turn in the rotation, while the reliever may get 2-3 innings in the same 5-day period. To me, this doesn't make sense.

The player I'm thinking of lately is Danny Herrera, who's been in the minors as a reliever. He's only got 39 innings pitched this year, while Homer Bailey has 69 and Daryl Thompson has 75. Over the course of a 4 season minor league career, that difference adds up to a couple hundred innings of valuable experience the reliever isn't getting.

Would it not be better to have your best arms as starters, and only after they reach the majors, weed out certain ones to be relievers?