There are too many good reasons to use your turn signals to excuse not using them. Not only are they an important safety feature and method of communicating traffic movement, their use is considered an act of courtesy. In many places around the world, the use of turn signals is legally mandated for these reasons, though in the United States, enforcement on turn signal use is often lax. In fact, not using turn signals causes twice as many car accidents in the U.S. as distracted driving, to a sum of two million crashes annually. Nevertheless, some seek excuses not to use this important feature of their car.
Some erroneously claim it not to be necessary, in spite of the above data, while others cite laziness, forgetfulness, or time constraints. Some may even think that the additional current draw on the alternator effects their mileage, and thus, costs them extra money. They're partially correct, too, as the theoretical cost of annual turn signal use has been calculated by a YouTube user.
Spoiler: turn signals cost you almost nothing to use. For those without time to watch the video, here's the breakdown. Taking into account the hypothetical energy usage of a turn signal, the amount of regular use a signal would see, and the thermal efficiency of gas engines in road cars, a hypothetical cost figure is reached: $0.29.
Even if this figure were off by an order of magnitude, the cost of turn signal use is still too small to excuse neglect. The full $0.29 can be recouped by things as simple as saving pocket change from a transaction or two, taking a coupon to the store, or even adjusting your driving style to use less gas. Drivers who face long commutes to work can easily save that amount in gas each day by adopting a thriftier driving style, or by keeping their tires inflated.
It costs you next to nothing, and it reduces the odds of an accident befalling you. A worthwhile investment, we daresay.