Right. Richardson has usually been higher on the scoring options list in his career. When he's with the starting unit and third or even fourth (behind Stoudemire, Nash, and whatever big man the coaching staff is trying to force-feed), he becomes more of a spot-up shooter, which isn't his game. His talents are better applied by giving him more responsibility to create.
This is an interesting observation. If true, and I'm not necessarily disputing, he would be one of very few that doesn't see improvement in scoring/offensive output while playing with future HOF Nash. When the Suns first acquired Richardson, we were excited about his 3-pt% and fastbreak ability. Those opportunities increase when Nash is running the offense...
It might be a combination of two things, #1 his level of concentration increases (or remains high) in direct proportion to the amount of time holding the ball. #2, he uses his speed to create more space when the defender is close to him as opposed to lunging towards his open jumper...
personally, I think its easier to hit a shot when the defender is going in a different direction, as opposed to jumping at you, regardless of distance. Furthermore, it takes a different type of mentality to "wait, wait, wait then shoot". Or to wait, wait, wait, then crash the board. Or even to "wait, wait, wait, then run back on defense"
(or in the case of the Suns, 'ease back on defense').
So when you say "it's not his game", it really isn't. So the Suns should put him in a position to succeed... that's why I support trading him