You should use turn signals even when there is no one around. At first glance, it seems stupid. Why should I turn them on, when there is no one to see them? There are two main reasons.
First, you never know if there is someone, you cannot see. A cyclist, a car in a blind spot, a car behind a bush. So it is smart to use the signal just in case you have missed something, to avoid a collision.
But, even if you would be 100 percent sure that there is no one around, it is still better to use them. Why? It builds the habit. You will not have to think about using them ever again. It will be automatic. Which means, you will not forget to use them when it is critical. And you will free your mental capacity, so you will not analyze all the time if you should use them or not.
The same goes for work stuff like documenting your work, writing comments in tickets, taking meeting minutes or setting goals. Even if there is no one to see them, it is good to build the habit. Even if you are a company of one or a team of one, you never know if there will be someone else joining you or replacing you, and the indicators will become critical. And again, you will never need to think if to do it or not, you will just do it out of the box, without effort.