Comcast has been doing this for years. And unless you get your own modem, theirs tend to turn the feature back on (even if you turn it off) automatically at various intervals.
The more annoying part is if your cell service is with Xfinity Mobile - their sim makes your iPhone automatically join Xfinity public hotspots, and there seems to be no way to turn it permanently of. It comes back on periodically.
The performance on these hotspots is terrible.