Having just passed my commercial checkride a few months ago, I can tell you the reasons I was informed of.

-Aircraft control
-Control Smoothness (this is key for most commercial maneuvers, passengers don't like getting jerked around)

I believe the chandelle is originally a combat maneuver aimed at gaining the most altitude possible, that is why it is low-g. All the aircraft's energy goes into climbing, none is wasted by pulling g's.

To successfully complete a chandelle you must master your aircraft. If nothing else chandelles are fun (I usually performed a few successive chandelles to gain altitude for a steep spiral).