I use HDMI on my Smart TV and just disabled wifi because I realized it was downloading more than half my bandwidth (a small amount, in fact). It could have been doing an update but I found no reason to leave it on. Occasionally I'll use YT or Prime since it doesn't have to be tethered to a PC, but overall it's nicer as a monitor than a streaming app.
Not that I believe it is used, but an ethernet connection can actually ride over HDMI. Possible to share your network connection by plugging in a display.