You don't need gears on an electric bike, but they can be helpful. New riders may benefit from the ease of single-speed cruisers, which are easier to get used to. However, if you're off-road, live somewhere hilly, or are doing long rides, gears can be useful. They work much the same as gears on a regular bicycle. It allows you to have better control over your speed and effort, plus it conserves the battery as well.