the problem is that most bananas are too weak for easy shipping. The first time this happened, years back (I forget the type of banana that used to be eaten and sold in the US), they settled on the Cavendish as a replacement because, despite being considered a very inferior banana, it was the one that could stand up to the shipping easiest.
Here's a very interesting interview on NPR's Fresh Air, with the author of a recent book all about bananas:
http://www.npr.org/templates/story/s...oryId=19097412