Most people don't buy their own router, the ISPs bulk buy thousands of routers at a time. The ISPs make up most of the market.
Many of these routers are managed by the ISP using protocols such as TR-069, several ISPs have already been found to not only manage the devices but also monitor certain data including what devices are present.
Many of these routers are managed by the ISP using protocols such as TR-069, several ISPs have already been found to not only manage the devices but also monitor certain data including what devices are present.