Some locks bind up. If you do not properly lubricate and exercise them, they can seize up and stop functioning. This generally happens on locks that don’t get used very often, such as automotive car doors(when the owner electric locks and remote) home doors that don’t get used much etc.
Normally this wouldn’t be a big deal, until you need those locks. If your car battery dies, and your door locks have seized from lack of use, your only options are to call a locksmith or break a window. If you have an attached garage, and have mainly used that door for entry, as many of us do, and your power goes out, your really going to hope your other door locks work properly.
Take the time to lubricate your locks a few times a year and exercise them a few times a week. Its worth it.