It happens because from normal use the potentiometer inside the joystick wears out. Usually you can buy joystick assemblies for a 1/10 of the price of a controller, so if you can solder its very affordable to repair them.

If you dont want to solder, you can extend their life by applying a bit of contact spray to the potmeters inside after disassembling the controller. But that can corrode other components, so be careful with it. Still beats just throwing them out.

But but but… Consoles are the AAA industry. Indies have a chance because of PC gaming.

How did that guy shave and change so fast?