They don’t belong to DTV. They are purchased by the consumer. The problem is that there is no way in hell DTV will issue a new (active) access card for an old receiver, when they can just refuse and sell a new receiver instead.
As the other poster pointed out, they are basically garbage. I threw mine in the dumpster.
You can sell them. I paid $20 on eBay for 2 DirecTV receivers to use in ice houses. Then activated them on my account. This was about a year ago. I don’t think any things changed, they should still be able to be activated on a different account.