I'm curious to know what those circumstances are. I'm just a dumb American driver but even I was taught you always use your indicator when changing lanes: turning, passing, merging, parallel parking. I don't know where at any point you are not required to use the indicator.
You are legally required to in the US.
Edit: I'm not entirely confident in this. You are legally required to signal a turn. Lane changes may not meet the definition of a turn. In NYS where I live lane changes are indeed included.
A relation of mine was renting a car with lane assist and it nearly drove him into the cones by way of refusal to cross the boundary (until it conceded control to the driver).
Sure, the lane centering systems don't know that cones change how the lane goes. They also don't know much about temporary lanes painted in yellow (in my country road works do this) and that they override the usual white lanes. Needless to say, one needs to increase their attention when driving through such things anyway, so I turn LTA and adaptive cruise control off and slow down. A wild road worker may suddenly appear in my way at any moment.
You are passing cyclists. Blinking serves two purposes: you are letting them know that you have noticed them (so they know you're not just going to plow right through them) and you are letting them know you are going to pass them (so they don't do stupid shit like decide to turn left at exactly this moment).
If a car behind me, in the same lane, was passing me without blinking, I would highly suspect a drunk or overtired driver.