Comcast has no vested interest in not sharing/re-selling my data. also it provides a stable IPv4 with geoip tagging that both serves to de-anonymize me and make it easier for third-parties to track me.

My VPN provider has a vested interest in not sharing or re-selling my data, if caught doing so it would cause a major loss of business for them and potentially permanently tarnish their reputation. Additionally they provide a stable IPv4 shared with many other users. Tracking is still possible, but is far less trivial and not so easily correlated with a county/state.

So I use a VPN. It keeps me safe from script-kiddies who might discover my IP when I visit their website. I provide free help for people having trouble with HTML/CSS, so I visit a lot of strange places.