Another winner is the person who gets to watch cheap digital TV, without putting together a usable antenna and limiting their reception to the broadcast channels that are nearby.
I mean: They just pay the money, plug the thing in, push some buttons, and: TV happens. Right?
Theres the question of whether or not the fraudulent advertisement clicking is using enough traffic to inconvenience or impose fees upon the user but otherwise I agree with you and am tempted to buy one just to fuck with advertisers.
Backdoors and spying are also a problem in theory except at this point you can't even trust "legitimate" companies on that front so it's a moot point.
You really don't want fraudulent clicks ("invalid traffic", per industry lingo) coming from your home network, because any publishers (apps and websites, per normal-people lingo) who use tools designed to block invalid traffic might start flagging legitimate traffic from your network.