There's nothing wrong with the first major scale pattern that most people learn on bass guitar.
It does the job great and you can make a lot of music using just that basic shape. Check out this lesson to see what I mean: Bass Guitar Lesson – Using Scales To Create Killer Grooves.
However, what if you want to take things up a notch? What if you want to expand the fretboard, have more note choices, play faster, break out of old and tired ways of playing, or come up with interesting lines?
Three note per string scale patterns will help you. I give you lots of things you can do with them in this video lesson.
Here's the free PDF to download and study. Make sure you understand how a scale is formed so that you can visualise the patterns within patterns that you get from all scales. Scales really are the building blocks of music so by making sure you know the patterns up and down the neck, you'll be arming yourself with the necessary information to get seriously creative.