Not only that, if you have home internet they will pimp it out to nearby cellphones because that helps patch up weak network connectivity in certain areas.
Comcast / Xfinity definitely does this. I have gotten many 'suspicious activity' CAPTCHAs on popular websites while using my home internet because of this. The routers provided by Xfinity are very locked down so you can't do anything about it.
Let's not even get into WiFi Motion which uses WiFi to track you inside the house. I'm sure it is enabled by default in most households [1]
Last I checked you can still turn this feature off.
You can get a gigabit router for $100 that works on xfinity which is worth it over their gear. Which is typically sub optimal anyway.