Because nobody holds them accountable for accuracy, SXM inflates their subscription numbers to include everything from vehicles sitting on a dealership lot, first year trial, streaming, and expired subs. Last most-believable figures I saw puts them at around 2% of radio-listening. That's if you throw in Pandora listening too.
Shouldn't SiriusXM's investors or the SEC be calling BS on the inflated subscription claims? I remember that it was common knowledge when the two companies were separate that Sirius' sub numbers weren't as close to XM's as Sirius claimed because Sirius was including radios in unsold cars in dealer lots as "subscribers" in its SEC filings while XM was only counting activated radios that were actually being listened to by flesh-and-blood humans. Once Sirius succeeded in hoodwinking the feds into accepting its takeover of XM as a "merger of equals," the phoney-baloney subscriber counting expanded to the XM side.