I don't watch enough Hawks games to judge, but let's just keep in mind what people in Boston have to say about Rondo. If you believe half the people here, he's a downright liability.
For all the talks about Rondo's attitude, he's never been seen yelling at the coach like Smith has. He has never openly defied a coach's instructions, like Smith has. And he has never had to be benched because of that, like Smith has.
Also, keep in mind that the bar for fanbase dissatisfaction with a player is different in Atlanta and Boston. Boston players are under a lot more scrutiny, but for someone to p--- off the Atlanta fanbase this much it takes a lot.
And for all the stats people are quoting on blocks and rebounds, there are others that tell a different story. How about a 48% true shooting percentage, which is lower than every celtics rotation player except Bradley and Oneal? How about 2.7 turnovers per game, which is higher than every celtic except rondo and pierce? Or that he takes more long 2s (from 16-23 feet) than any celtic? Smith attempts 5.9 field goals a game from 16-23 feet and makes 32% of those. For comparison, KG tries 4.8 from that distance and makes 46% of those.
Now, you could chalk this up to inexperience or youth, but the guy has been 7 years in the league. Every coach he's ever had has asked him to shoot fewer long 2s. Everyone in Atlanta has asked him to do that. People yell "no" in home games when he lines up for these shots.
He is a hell of a talent, and very athletic. But he simply does not play to his strengths and no one has seemed to change him. To bet that Rondo and Doc would change him after so long in the league is too much risk. I'd rather risk it with cap space and picks than giving up anything meaningful for Josh Smith.