I don't see many citizens in my area lamenting the lack of tanks, Gatlin Guns, Half-tracks, or flame-throwers(M7a1) either.
The "just because" legal argument seems a bit of a stretch but as noted, if a WA resident wants to lay out the $$$ & wait for a "can" then so be it.
I can think of a few more pressing 2A issues or legal conflicts than SBRs & sound surpressors.