It's because LED's take VERY little power to lite-up and there is always a small flow of electricity flowing through. You CAN fix this by installing a resistor(s). The highER quality lights usually come withthe resistor already installed. Mine has been in and dinmly on for years now, you get used to it. It's not worth the hastle of installing a resistor if you ask me.
2006 Focus ZX3 SAP, Draxas Header, FS Werks Flex pipe, MBRP exhaust, CAI, Tuned, Debaged, tinted windows, FRPP lowering kit, SVT 5-spoke wheels, Black Halo Projector Headlights, Niteshaded Side markers and tails, Mazda rear wiper, mustang antenna.