It's all about service...
Normally, my wife and I spend most of our time outside of the hotel when we go on holiday.
On this holiday we ventured out only three or four times, but otherwise stayed at the hotel and enjoyed the service. If we were not at the pool side, we used the spa services where we enjoyed a session every second day.
I think that, if the spa staff are as good as Stephano and Dimitra, it is like adding one or two days to the holiday.
Even though the hotel was booked to capacity, Alex and the two managers we met (both called Maria) always had time to help or support. The waiters got to know our room numbers, preferences and where we liked to hide by the pool, (Christos and Serjio mostly).
I've stayed at some pretty nice hotels in my life, I can see why so many people return to the King Jason though, it was very, very relaxing.