This is a new one! Comcast doesn't want their customers to buy their own routers. They like the revenue they get from leasing routers to their clients. If Comcast customers don't use a Comcast router, they are faced with Comcast popup appearing during the course of their web browsing. There is a support link on Comcast's popup to indicate "approved" routers. Why not let free market and customers decide which router to use? Notice also that there is no way for someone to opt out of these messages or the ensuing phone calls.
REALLY! At Bullitt, while we sell affordable routers which we can easily support, we don't offer a lease program because we don't believe in them. We also do not mandate that you buy a router sold by Bullitt.
Check out the article: https://consumerist.com/2016/01/12/why-is-comcast-interrupting-my-web-browsing-to-upsell-me-on-a-new-modem/