Man on 1st with 1 out becomes RISP with 1 out. That is a flat-out worse situation. Take a look at the run probabilities. If it were really as clear-cut as you make it sound, Burnett would IBB whenever there was a runner on first, but he doesn't. It's all about who Wright is, and he is not enough of a threat to make it worth IBBing him. Besides that, Burnett is not just a GB guy, this season he is also a strikeout guy. By IBBing someone you completely eliminate the potential for the K, which is obviously the best outcome.
Except that's not what the situation was. Reyes was on 2nd with 1 out. First was open. If Reyes had still been at first, it would have been a whole different situation.
