Because they are broken.
Fuse or windshield wiper motor.
Windshield wipers are an important safety feature on cars. They stop working when their motor goes out, or when the blade is too worn out.
Normally its a fuse. Check your owner's manual to find where the fuses are and which one is related to the wipers.
burnt fuses
Blown fuse would be my first guess.
Blown fuse or bad wiper motor.
your windshield wiper motor might burnt out or a fuse might burnt out
The most common cause that windshield wipers stop working is a blown fuse. The windshield wiper motor may need to be changed is also common.
A cars windshield wipers should work either way. They should word with or without wiper fluid.
There are several things that you can do to help stop your windshield wipers from squeaking. Clean the wiper blade often to remove dirt and debris. Squirt windshield cleaner fluid on the windows to remove dirt. Ensure that the wiper is screwed in correctly. Replace the blades when it is needed.
It needs to be checked out . There are many things that can go wrong.
Check your fuses.