there's an article on Seeking Alpha that basically says it's their retention policy that hurts revenue.

"A much more likely explanation is the continued and growing use of retention discounting. At the Citi conference referenced above, Liberty Media (LMCA) CEO Greg Maffei presented yesterday, and was questioned about Liberty's plans with Sirius XM. He was asked about the extensive use of retention discounts by Sirius XM and whether investors should be concerned that a new CEO would discontinue the current practice. Maffei replied that the Sirius XM business model was currently working well and that he didn't anticipate changes."

full article here