I went to the site and found some interesting infomation you didn't present.
The column in the far right only tells you the +/- POINTS Differential when he's in the game, usually with the Big Three so that stat is somewhat biased in his favor. Besides, it's not very applicable when you figure that in some blowout games our first team is out and the scrubs in while the other team has its best out there trying to comeback.
Much more interesting is the stats/rating you don't mention:
Help Value (which is rebounds, blocks, steals, TOs per minute) Of all the roster, he is better than only Butler and is a very far behind most of the other players.
Productivity (which adds Points to Help Value) Again, he is the lowest rated Spur with the exception of Butler. Outside the Big Three, most of the rest are in the .50s range. Bowen is .36
Efficiency Rating: Adds up everything in the stats. Once again, Bowen is next to dead last Butler.
These stats say he's behind Beno and Williams, not to mention the rest of the bench, in every category.
Stats aren't everything, but its pretty obvious that Bowen isn't giving us much but defense. And when you are giving up 20-30 points differential against a great player, I'd rather let that guy try for 50 and wear himself out defending his counterpoint on the Spurs for a change.
No one ever mentions that most teams leave Bowen alone because he isn't much of a threat. They can afford to play 5 on our 4 and let him have his occasional 3.
I like Bowen's defense--but this site was an eye opener that confirmed what I'd been intuitively thinking. Bowen's defensive abilities may not be good enough to overcome his other liabilities.