Sleeping on your back is a boon for spine and neck health, because the back is straight and not forced into any contortions. Plus back sleeping helps the matress do its job of supporting the spine. Ideally, everyone should sleep on their backs without a pillow, as this position leaves the neck in a neutral position, although this position can be quite uncomfortable.
Another benefit of sleeping on your back is is that your face is not squashed up against a pillow the whole night and this sleep position leads to fewer facial wrinkles! Who could have thought that a proper sleeping position helps in your beauty aesthetically?