Several reasons. The first is the 1-2-2 seats just seemed more comfortable to me. Secondly, the "A" seats on the 1-2-2 configuration had a "glove box" in the right arm rest which a) allowed you to very conveniently store lots of stuff, and b) caused the aisle to be further from your body resulting in fewer bashes by clueless passengers carrying large bags slung over their shoulders.

And finally, the extra space on the 2-2-1's because of the lack of a glove box anywhere on the row was used up by wider aisles and more distance between the fusealge and the window seats. This is fine, except it made it harder to jam a couple of pillows between so you could rest against the seat, the fusealge, or somewhere in between. On the 2-2-1's I always kinda fell into the hole in between, typically waking suddenly (and unpleasantly.)

But as I've said, I've made my peace with the pods.