There are many benefits to playing scales on a single string. As well as helping to learn the fret board, it cultivates in us an intuitive feel for the way scales are constructed (the order of whole steps and half steps).
Technically, it helps us get used to the differences in fret width as we ascend and descend the fret board. It also makes us develop clean, smooth position shifts.
In this video, the single-string scales are played with hammer-ons and pull-offs, first normally, and then in triplets.
There are many other things you can do with single-string scales. Try playing them on different strings and experiment with different scales and modes. Have fun!