The short answer is most people don't handle change very well and will not change their conclusions or actions based on new evidence.  The process is:

1.  Ignore the New Evidence
   
2.  Deny the New Evidence
   
3.  Reject that the New Evidence will affect them in any way
   
4.  Reject that the New Evidence will affect them to the same degree

Now add the fact political and other Decision Makers are highly addicted, physically and mentally 'attached,' to the status quo and it's easy to see why the EU is in a Real Mess©.


She believed in nothing; only her skepticism kept her from being an atheist. -- Jean-Paul Sartre