Well, it has to do a lot with support. Directv needs to provide direct support for at least a couple of networking options besides sticking in a wire. Your best bet is to select one or two widely sold, name brand products, offer your support for those products linked to your box, and hope to improve customer satisfaction. While powerline devices are pretty much plug and play, wireless bridge adapters seem to find a way to be about as complicated to configure and use as a product can manage.
Good choice to provide support and configuration assistance/advice to a couple of products in hopes of improving customer satisfaction, or at least steering the customer to some good choices.
Otherwise, we know what they do. Pick the cheapest dang thing they can buy that someone else says worked for them.