The only reason I can think of that you would need Priority Boarding is if you travel with carry-ons that you absolutely must have on board with you. If you do not have Priority Boarding, there's always the chance that the overheads are full by the time you get on, and they will make you gate check your carry-on. This happened to us on the return from Orlando home last year. It was no big deal, but then we had to add an additional 20 min. in the airport going to the baggage carousel to retrieve our carry-ons. Had we not had to gate check them, we would have been straight to the car & on the road more quickly.
If that's not important to you, don't pay extra for Priority Boarding.