It goes to show just how insufficient their network is. They have no confidence in it.
It has nothing to do with the network. They lost a lot of money when Apple introduced iMessage, and they don't want that happening again with FaceTime. They can't go back and charge people for iMessage since it's now too late, but they can charge for FaceTime going forward, and they will.
The lesson they learned is to block any app or device that can cut into their revenue stream. They are opposed to technology improving our service and reducing our costs.