It's not much that the point: did you notice your phone lighting up the screen when you move around it? That's not much an "image" capture threat (meaning you covered the phone cam and allow the other sensors in that example) but a "person presence" and "person activity" threat.

Essentially with apparently innocent and cheap sensors you can determine what happen in a home, perhaps selling some smart bulb who can just tune the light and light on automatically when you enter a room then turn off after a short period of time. Apparently a simple and innocent comfort idea, but also a potential cheap remote spying device.

We already know some "strange" attacks like discovering keys pressed on a mechanical keyboard via the produced ambient noise, any of such potential threat alone seems innocent and low risk, but put together allow for a potentially cheap mass surveillance inside homes walls in a far less monitored ways.