Earlier quoted context omitted.
It's like using your turn signal even when you know there's nobody around you. Politeness is a habit you don't want to break.
That's an interesting example to use. I only use turn signals when there are other cars around that would need the indication. I don't view a turn signal as politeness, its a safety tool to let others know what I'm about to. I do also find that only using a turn signal when others are around is a good reinforcement to always be aware of my surroundings. I feel like a jerk when I don't use one and realize there was so…
This has a failure state of "when there's a nearby car [or, more realistically, cyclist / pedestrian] of which I am not aware". Knowing myself to be fallible, I always use my turn signals.
I do take your point about turn signals being a reminder to be aware. That's good, but could also work while, you know, still using them, just in case.