Why are scales important?

If you start a piece of music with the realisation that it is just a unique arrangement of patterns from scales then you will discover the importance of learning your scales. 

Understanding the scale or scales that relate to a piece of music means your fingers will automatically recognise these patterns when you play making it easier. This also helps you to recognise where the piece will most likely modulate to (Subdominant, Dominant or Relative Minor/Major).