🚀 go-pugleaf

I think it's more for their protection than yours - and with a cable network lightning isn't very likely to happen, quite frankly. It does also slightly protect them from you sending a raised potential back down the line due to faulty equipment at your end, but this also isn't very likely.

Why only one room? Because everything else connected to your cable installation is effectively isolated at the point of contact, is the usual reason. Ground loop problems don't always make a lot of intuitive sense - sometimes it's quite difficult to work out where the stray noise is actually being introduced to the system. Almost invariably it manifests itself when grounded audio connections are made, and hardly ever troubles any other equipment at all, simply due to the fact that they all use effectively isolated connections, especially at RF frequencies.