When looking at new build houses a year or two back (in the UK), I saw some stuff that made no sense to me: they installed some by default, but ran it to only the lounge and bedroom 1, the house also had a dedicated study (labelled as such by them) which did not have an ethernet run to it, and they refused to let you option in any more, very weird.

It's for the TVs, to provide network for live TV boxes.