Because prep pitchers are ridiculously risky as a whole? It's a big gamble to devote that much of your draft spending pool on the most volatile asset in the mlb draft. There are also injuries, unrefined mechanics, projecting development of secondaries, body types, etc that of course come into play as well. I personally am with you on just taking the guys you have rated highest, assuming they fit the budget, but I get the thought that you could get 2 hitters you really like in the 1st round, save some money, and still get a high ceiling lottery ticket pitcher in the next round.