Why do the towers use ramps instead of stairs?
(And speaking of it, all the other adventurer mode buildings.)
I think of the X stairs as more rickety spiral staircases, but aside from the tower, the only one I can think of is the new labyrinth, which uses stairs. I also didn't like the thought of a battle being fought up a tower with the defenders always being directly above in a row, especially if arrows work down through multiple stair tiles.
I'm not sure where the "rickety" comes from, as most castle spiral staircases are extremely solid. Aside from the space-saving properties, the defensive design was significant; the usual spiral was arranged so that right-handed defenders above could brace their shield against the central column, and swing their sword in an arc that worked with the arc of the stairs, in addition to the advantage conveyed by height. In contrast, attackers from below were at a height/angle disadvantage to start with, but additionally had a much more restricted arc to operate their sword due to the central column, and no easy way to brace themselves against a shove from above. The design also prevented more than one rank of attackers being brought to bear, as the spiral broke line of sight for ranged weapons and rendered polearms too unwieldy to be practical (if they would even fit at all). In short, they were ubiquitous precisely because they were a major architectural element that allowed one well armed man to quite literally hold off a small army, as they were forced to come at him one at a time under seriously disadvantageous conditions.
An excellent ancient example of a spiral staircase for reasons of space rather than defense is
Trajan's Column; while they were used occasionally beforehand, its construction in 113 AD vastly popularized the form, and it remains sturdy today nearly two millennia later. Even when constructed of wood rather than carved or constructed of stone, they can be quite strong; see
this example from Salisbury Cathedral for example.
Of course, as castles evolved into chateau and thence into stately homes / mansions, the staircases evolved as well. Being able to put in something like the
Chateau de Chambord double helix stairs in would not only provide potentially better pathing, but an attractive and interesting architectural feature to set an elaborate building or delving above the ordinary.