When this was legalized back in 1996 ,two concerns that arose of expanding to the shotgun was :
(1) gives QB a quick glance to see if any receivers are open;
(2) bad airborne snap could be fielded and spiked by QB to prevent sack.
IMHO, those two concerns still are there and a few years ago it was learned that the NFL prohibits the shotgun spike for the same reason.
1) There is no QB that is quick enough or smart enough in high school to do this. If they did, it would look something like this:
https://www.youtube.com/watch?v=cMN4nYAIdeI2) So what? They were going to spike it anyway. Besides, if you muff it, you can't legally spike it. Case book 7.5.2B
Also, I know we don't like to use the "C" word when making high school rules, but the rule has been in College for many years with no issues. 999/1000 they are going to spike it when they receive the snap.