Because lunch is never long enough.
Lunch is the highlight of most students' days. It's one of my highlights too! Let students enjoy more of it with an early lunch dismissal. This doesn't have to be crazy! Even letting students go a minute before the bell can feel like a big privilege. You might also consider letting students pick a friend to go with them.
There are many ways to run this reward !
You can even think about rewarding teachers with this too. Step into their classrooms to give them a longer break.