Because vandalism, destruction of public property, and violent lawlessness are generally not well-tolerated in this country.
P.J. O'Rourke had a brilliant line in one of his essays on Somalia- it went something like "In Mogadishu, everything that can be accomplished with guns had pretty much already been done". He was referring to the utter destruction of the city and the society.
We are not Somalis, and we don't settle civil problems by pulling a gun out of the trunk and blasting away. And, having served in countries where they DID "settle" problems that way, I am glad that we don't.
For example, there weren't many tears shed over Romania's last dictator when he was publically executed.
I challenge you to come up with 10 people who have been trapped by these bloddy devices who think that they are a really good idea and theat we should install more of them.
The general population may not actively support a person who destroys them, but they probably won't go out of their way to help apprehend them either.