You want the real answer?
It was not working out properly, and created more problems than they could iron out in time. It was buggy as ****!
Happy?
Plus I am sure they want to hold off on too many franchise implementations of features until they redo the franchise mode like they have planned. Why add and complicate a "legacy" mode with coding when you can implement things with a new rebuilt mode?
Not really that hard to understand. These guys do not beat around the bush.