Why should people drive cars with manual transmissions?

People should drive cars with manual transmissions because it forces drivers to be more engaged while driving and lowers the incidence of distracted driving, making it the safest choice overall.

Environmental concerns about fossil fuels aside, one of the biggest issues with driving today is distracted driving. With improvements in cruise control technology and other driver assistance functions like lane keep assist, cars are taking over more of the driving process than ever before. While the intent is to make it safer for drivers, it also has the unintended consequence of making easier for drivers to be distracted. 

Cars with manual transmissions not only force greater engagement and focus, but they are also either incompatible with, or only compatible with lesser versions of, certain driver assistance features like adaptive cruise control because lowering the speed while not being able to change the gear (which is manual) could cause the car to stall. 

Paradoxically, by increasing the required inputs and decreasing the number of driver assistance features, driving a manual transmission car is safest.