I'll move this to General Cruise Chat since it isn't an RCI-specific question.
No, I don't always go someplace different. We've done probably 15 cruises to the western Caribbean. It then becomes more about relaxing and the ship than it does the ports, although I am quite fond of Cozumel. Why so many western runs? Logistics. I can drive to two ports on the Gulf Of Mexico, but ships leaving from New Orleans and Mobile are limited by distances so they can only do western Caribbean itineraries.
For a getaway cruise, I really don't care about the itinerary.
Of course, the logistics for you being in Ireland are entirely different. You'll always have to fly someplace to cruise.