It is not bad to always use them (if you are using them correctly with the correct products) but it not necessary IMO. For compounding/polishing out surface imperfections they are terrific. For waxing and wiping clean there is no need IMO. It takes longer for me to use a machine to do a simple wax job than it takes by hand.
Let's not confuse terms. What machine are you using? What application pads/bonnets are you using? What products are you applying? What are you using to remove them from the paint?
Run a search in W&W for the term "buffer" and you should come up with several threads.