I mentioned it somewhere else, but HDMI can carry an ethernet signal. They could potentially in the future show ads without having to deal with the OS at all. Of course you can just disable the network but most people won't know how.
HDMI can have ethernet as well, though I'm not sure how common (if at all) it is to route this through a normal video card. That might change if LG asks Asus nicely.
"Ads and OSes could one day help drive down the price of monitors, as they did TVs." - Don't buy into this. Ads don't meaningfully affect the price of anything. It's just free money for the company and they can charge extra as a "no ads fee" to the people that don't want them. They're not getting hundreds of dollars per person.
It's an oligopoly. They do this because they think that prople can't go to a competitor because Samsung is doing the same thing. The people that's supposed to keep this from happening hasn't been doing their job.
The fact that it improves safety is a claim that can easily be challenged as recently it seems to have put people in harms way. Texas police used it to stalk a woman across state lines to find out if she got an abortion elsewhere.
Insurance in general should be a public aervice rather than private enterprise and it should not be used for medical care at all.