What makes you believe that?
Well, the main firearm for police is the sidearm. The weight that a suppressor adds makes the gun more difficult to handle. Granted, my only experience is with the old fashioned suppressors with the rubber grommets, but I don't think the new suppressors are that much lighter. Additional weight at the muzzle of a handgun may not matter in target shooting (my forte) but it really matters in tactical situations.
When you hear the evidence that suppressors make a weapon more accurate, it's always in reference to a stationary firing position.
Also, the new types of suppressors are much less effective in quieting a weapon. Even the volume of a suppressed weapon is enough to cause hearing damage (it's the attack portion of the envelope that causes the damage as much as it is the volume).
Of course, this is not viable so long as silencers remain regulated and taxed as heavily as they currently are in US (much more so than guns themselves).
I'm pretty sure the suppressor regulations are local, not national, by the way.
If anything, local police are too eager to go to their weapon to solve a problem as it is. I'm not sure you want to encourage more of it by making gunfire quieter.