The argument that won the day in WA State was hearing damage. It was pushed by LE, and should be pushed by LE as they probably are inpacted more than anyone else.
I will give you an illustration. LE and other shooters have been trying for years to get a large indoor/outdoor range built in the proximity of King and Snohomoish counties. They finally came up with a plan where they would build this facility on State land in a valley in the mountains between Arlington and Lake Cavinaugh. They still had enough opposition (mostly from lakefront owners) because of "noise" (and traffic) to kill the plan.
If they had done the tests with suppressed weapons I doubt you could have heard anything at the lake. As it was all you could hear was an occational pop.
Suppressors probably would save some other ranges from noise complains too.