In my opinion.... Because of chainstores like bestbuy, circuit city, and walmart. Consumers who shop at these places don't have the knowledge to fix issues/install on their own stereo so they listen to whoever sells them their stuff to get their knowledge. Most of those sales people work on commision, they'll bullshit from the moment you walk in the door in order to get a few extra dollars on their paycheck. Dude at bestbuy tells a person that a capacitor is exactly what they need to stop headlights dimming, that person tells another person, and so on. Plus capacitors are flashy, contain led's and voltage meters sometimes and for some reason every 16 year old wants one cause its 'cool'. Just my opinion though.