I recently visited St. Lucia on an NCL Gem cruise. St. Lucia was the third port stop and we actually went on an excursion!
As a promo when booking the cruise, I had $50 credit for excursions which made me more inclined to go on one. I still didn't want to spend a lot of money as it's $50 total for me and Husband, not each, so I looked at the least expensive options in each port...