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.
This is pure anecdata, but almost everyone I know, include the people who aren't particularly computer-savvy, owns their own router and cable modem so that they don't have to pay a rental fee to their ISP.
