they enhance the sound when you play, like on my my guitar, the kramer striker special edition, when on the bridge pickup, you get a high pitched buzz, rockstars usually use this with distortion. when playing other styles you switch between pickups to get a different effect on the sound. i admit it is hard to notice at first. but when you have acoustics and stack amps projecting your sound to people at a gig, you notice the difference between them. i used to ask myself the same question, so being a complete idiot, i removed the pickups and tried to play, it sounded like trash.