LEO are using M&P's over Ruger's. Enough said!
That doesn't mean anything.
A large percentage of law enforcement agencies use Glocks as well, but there are plenty of polymer designs that have long since surpassed the Glock in almost every respect (M&P pistols, Walther P99/PPQ, XDm, and any number of CZs and H&Ks spring immediately to mind).
However, Glock markets their pistol heavily and effectively to LE agencies, offers them insanely low unit prices, and very desirable service contracts. S&W has recently began to mimic Glock's success in the market, largely by taking short-term losses (for example by offering to exchange Glocks for new M&Ps).
My guess is that Ruger doesn't even try to market to LE agencies (or the military) because they don't have to.
As of April of this year, Ruger stock was up a whopping 571% from November of 2007 while the S&P 500 was down 3%. And they did this without any significant military or law enforcement contracts.