Perhaps because the Suns can actually shoot?
Outside of an inconsistent Deron, who on the Jazz could put up a reliable jumper? Miles rushes his shots under pressure. Boozer has performance anxiety; he simply can't get it up against the longer Lakers. AK? Matthews? Well, Wesley is o.k. as a 3rd/4th option.
Formula remains the same for Jazz opponents: double on Deron's penetration and let the Jazz SF or SG have the outside shot. Pretty simple.