In addition to what DavRob said, the Fett model clones were NO LONGER the main complement of Stormtroopers by 0 ABY (aka the year "A New Hope" happened).
... Thus, the Fett clones were ironically reduced to a minority status after years of virtually filling the stormtrooper ranks in its entirety. According to a stormtrooper's entry log in the 501st Journal, none of the Fett clones were ever truly able to come to terms with serving alongside recruits and different clones, all of whom were disdainfully dubbed as the "new guys."
Commander Cody, a first generation clone of Jango Fett and a veteran of the Clone Wars, found stormtrooper recruits to be absolutely intolerable. Due to the significant decrease in the Imperial Military's operational effectiveness and his own feelings of nostalgia over the Republic's "army of one man," Cody viewed enlisted troopers as incompetent idiots, all of whom he would have gladly sacrificed for just one real clone trooper. (src: The Force Unleashed 2)
Please note that, leaving this aside, the troopers that Obi-Wan "hand"-winked into thinking these were not the droids they were looking for were some sort of random patrol from a garrison on backwater, a$$hole-of-the-universe planet. For some reason, I have a feeling they were kind of the worst of the worst - sort of "If you tick off the officer you'll be serving the rest of the term on
North PoleTattooine garrison".