Why do we fit skirting boards to collect dust?
Wikipedia
  
  In architecture, a baseboard (also called skirting board, skirting, mopboard, floor molding, as well as base molding) is a (generally wooden) board covering the lowest part of an interior wall. Its purpose is to cover the joint between the wall surface and the floor.
  
  https://en.wikipedia.org/wiki/Baseboard


The purpose of a baseboard is to easily cover the joint so that it does not have to be seen. It's much easier to finish the plaster and then tack on the board that take the time to ensure everything is flush and not get any plaster onto the board. I don't believe that they are "designed" to collect dust, that is simply a side-effect of using them.