Agree with Pos. Like he said, a player who handles the ball more will turn it over more. But TA isn't asked to handle it that much. Pierce had a turnover ratio of 11.7 last season. Allen's was 16.2. The year before, at 15.8, TA ranked 62nd out of 63 2-guards in TO ratio, so he's among the worst in the league at his position at turning the ball over/handling the ball. He sucks at it.
The only rotation players on the team with worse TO ratios are Perk at 20.2 - mostly because of his illegal screens and the fact that he's a center with not the softest hands - and Marbury, tied with TA at 16.2. To Marbury's credit, though, he had always been around 10 in the TO ratio department throughout his career. Allen, on the other hand, has been above 14 the past 4 seasons.
Interestingly, there was a non-rotation guy with a higher TO ratio than TA - Bill Walker, 18.2.