Just to give you all an insight as to how players can get spiked in the face, I will relate two experiences my son's team had last year. Both times the spiked players were playing third base when runners were slidding into the base head first. Just as the tag was being placed, the legs of both runners came up over their back somewhat like the tail of a scorpion. One player took 22 stitches, and the other one, my son, ended up with a broken nose. By the way, both players got the put out.
I thought it was a once in a life time occurance, but to have an accident like that to happen to the same team in one season was unbelieveable. Go figure.
To answer the orginal question,I believe they are necessary. Most fields the HS play on are not Camden Yard quality. Most are tightly packed dirt, and without the metals cleat's ability to cut into this surface most players would look like they were on ice skates. Besides, this a player's right of passage to the next level of baseball. Little league rubber cleats, now metal cleats. Accidents will happen, just another facet of the game.