TV manufacturers will then detect this and remotely lock the user's TV for breaking their ToS.
And miss out on ad revenue? No, they'll just silently mark your warranty as void and continue to force feed you and your family targeted advertisement while siphoning out all the private data they can gather from your living room and your network.
Why not just a curtain of black fabric? Spray paint requires some skill to apply consistently and without waste, whereas a clip-on fabric is far harder to screw up and less likely to void your warranty.
Or they can add an e-ink panel behind the main panel(s).
Or the front of other's transparent TV's used to advertise to you.