I'd imagine that there are all kinds of complication from implementing it that the risk is just to high.

For example, they probably use the party flag to determine if you should be removed from duty finder (invite a friend and it will drop you from queue). If you are queue'd with a companion and are set as "in party", then if you invite a friend, the system will not know to kick you from the queue. This would require a complete re-work of how they flag for when you are no longer eligible for duty finder. If your companion does not form a party, then they will have to re-work the party limitation for when companions are out. Either way, major bugs would need to be addressed.

Throw into the mix that they could be developing all kinds of changes to companions or an alliance system and the effects become un-imaginable.

It sounds like they are waiting for development of the expansion to settle a bit before deciding on the best way to approach the issue.