You might be trying to hang a set of pictures along a single wall, but you don’t want them to look lopsided. With a standard leveling system, you could have a problem. It’s impossible to hold your level against the wall while you’re hammering a set of nails. You would need an extra arm, and you don’t have one. So, you would need to have a second person to help you with the job. Laser levels make it easier to do these tasks. And in many cases, they don’t require a second person.