If I was a shady business, a nefarious government, or a malicious hacker and I wanted to eavesdrop on you, I would probably attack the vector that spends much more time by your side and can easily hide its data connections from you, e.g. your mobile phone. As long as these home automation devices ride on your own personal network, it is easy to monitor to what extent they are sending data back home.
My argument is that you should prioritize your worries and these devices are a lesser threats than phones. To use your analogies, I wouldn't worry about tightening my seatbelt or getting cancer if I am in the back of an ambulance on the way to the hospital for some other life threatening issue.
Or perhaps a better analogy, I wouldn't stress about keeping the windows of my home locked if I never locked my front door.
