While it's not always necessary to have a tripod for low light photography, it can certainly be very helpful. When shooting in low light, you typically need to use slower shutter speeds to let in enough light to properly expose your image. This can result in blurry photos if you're not able to hold your camera steady for the entire duration of the exposure. Using a tripod can help you keep your camera steady and avoid blur caused by camera shake.
In addition to helping you avoid blur, a tripod can also allow you to use lower ISO settings, which can result in images with less noise or grain. This is because you can use longer shutter speeds without having to worry about camera shake, allowing you to use lower ISO settings and still get a properly exposed image.