If you take for instance an all-round bike like a Honda CB500F, if the preload is setup soft, you get a more comfort suspension behavior for things like touring, but if you setup the suspension much firmer you get a sportier setup, you can take turns at higher speed and deeper lean angle…. But you lose comfort, more and more you feel the bumps in the road…
You can get some explanation on how your suspension works for an article called Adjusting your Motorcycle Suspension
What are the advantages of softer vs firmer settings?