HugoNoob:
It seems to me that none of the Showcase sites use themes. Do the sites pre-date themes? They seem to be mandatory now – if I don’t specify one, nothing happens.
I think it’s a matter of choice.
Having no theme means you put layout files directly under /layouts, all the styles under /static etc.
Themes is convenient to get up to speed fast.
That makes sense. I have a tendency to shave yaks 
so I was hoping to leverage themes, but I don’t see any example sites that use them.