Found it to be a user setting which defaults to "on". This is really dumb imho 
and annoying because this also means that you need to have an account and be 
logged in to be able to see all changes. 

what is the name of the setting?

Preferences/Recent changes and stub display/[x] Show only current revision of  
pages in recent changes view  
  
In my opinion it's a major usability problem that this option defaults to "on" 
and that "Recent Changes" doesn't tell you when it's showing a shortened view. 

i like the current behavior better as a default setting. as the number of items 
shown in this list is limited, i dont want to waste space for multiple changes 
to the same site. i think most people are only interested in general activity. 
if you want to know the detailed list of changes you can still go to the history 
 of the page.