Ruger hasn't offered to exchange department Glocks for new SR9s, in pursuit of LE contracts. Smith & Wesson has shopped the M&P very heavily, and taken short term losses to get those contracts. Manufacturers who opt to do so compete for business. LEOs aren't voting for favorites.
'nuff said' only works when the statement tells the whole story.
Currently Own: Beretta PX4 9mm, Glock 23 (Gen 4), Glock 19 (Gen 4) x2