Why is it necessary to rob me of my inputs when cancelling construction?

[Ashrem]

I get the decayable materials, to prevent manipulating decay, but why is it necessary to turn my planks and elixir in to supplies and coins when I change my mind fifteen minutes after starting to build a bunch of extra Beer Festivals and Tea Houses? This is the kind of thing that can cause people to rage-quit, so why do it?

 

[The Fairy]

I don't know, but my guess is that they have implemented cancel building as selling a building, so you only get the resources back that you would get if you sold it after finishing building it.

This can be a benefit in special situations. In chapter 19 you need to build a lot of expiring buildings and get some guest race goods when you sell the buildings. If you don't cate about the goods they produce before they expire (these goods can be produced with portal profits), then you can start building and sell immediately before the building has finished building.