Yesterday I forgot to save a complex drawing in yEd and later I left the application lying in the background on a virtual workspace. Later when I shut down my computer everything got lost, because yEd neither prevented the shutdown nor auto-saved my work.
Looking - for example - to my current text editor, which is saving even unsaved and untitled documents on every change, I'm now used to never think again about losing any work at any time, just because I accidentially changed my attention to something else and then miss to save my work before.
I think this should be the behaviour of every modern application!