First of all, there is risk involved in every draft pick. There is just more risk involved in HS players/pitchers. However sometimes the potential reward is so high that it makes the risk worthwhile. The draft is a guessing game.
Even though not many HS pitchers have been the first over all pick, HS pitchers represent a big percentage of the first Rd nearly every year.
Name whoever one thinks are the best pitchers in the game today and see if they signed out of HS or College. I'm sure whoever someone would list as the best, there would be some that signed right out of HS. Same thing goes for position players.