Apparently their suites sell out (and, of course, many do the Move-up bidding, freeing up a lot of cabins in steerage). I don’t think the infinity cabins on Edge class are popular, either, and most of the balconies are just that.
TBH, DH and I have just been discussing the fact that we don’t need the Retreat on X. We’ve booked it for September and will maybe only dine in their suite restaurant on one night 🙄. We’re not ones for hanging out all day on the pool deck, so we probably won’t even use the Retreat one much. Only reason we booked a suite was because it’s our anniversary - and we got a good price at the time of booking, with some nice perks.