I was wondering the same thing. Sirius are only open to subscribers and now this one:
https://capitalonebigpayoff.com/en-us/Rules?linkId=42732367
So, I guess if they don't offer to sell you anything, they can limit who is eligible
I would like to discuss these. I have subscribed to the daily amazon notices and I get 137 pages (15 per page) Many many are duplicates...some 15 times or more. Now, these only last 24 hours and only give prize to 1000th entrant. And I noticed the higher the page number, the better the prize...