answer:Because of the type of circuit used. This is called a parallel circuit. Compare voltage to water pressure. If you would poke multiple holes at the same height from the bottom of a bucket full of water, then all holes would remain to have the same water pressure. The pressure only changes when the overall water level of the bucket drops. If the bucket is big enough and as long as there isn’t too much water flowing, the pressure at each hole stays the same, independent from other holes you’d poke in the bucket.