The reason to use a lens hood

Hoods that come with good quality lenses are designed to reduce glare on the lens when shooting outdoors in daylight. But many photographers, including pro, keep using it in indoor, with reason, to protect the lens.

The glass lens, almost parallel to the end of the barrel. When the lens is in contact with something, and this object was not soft, your lens will be scratched, in worst case it could be broken, addition lens hood can also prevent stains fingers, because we accidentally touch the tip of the lens.