Comment by Shiballllllbaaaaaaa on Witch Hat Atelier - Chapter 61

if they are in the habit of doing something else
if the systems encourage a different use
if there is a high cost in switching 
if they don't travel the slums and know/experience/understand the problem... I doubt many in the crowd saw the vases and linked them to the slum problem

Humans are not naturally selfish it's just we are encouraged to be so. To claim we naturally are shutsdown the ability to change the situation.
And I would argue that love is the glue that binds society together. When humans at large fully believe in selfishness ethos then you don't have a society anymore.