During first levels and through many game implementation players built lots of towers that maybe they will not use any more, or maybe 1 time every 2 years when a strange war boost appears.
The purpose is to make “towers” changing similar to “clothes” changing, it would be great if game let players dismantle an old tower in order to get - gold? pearls? stone for conquest? - something useful, however more useful than the tower itself.
I suppose it can speed up new players, who can obtain resources from old towers for new towers when they unlock them, and it will cost less sufference if new towers will be avaible and we’ll have to change path or combination.