Function based views don't support HTTP HEAD method by default

[Doomse]

I recently noticed that the default value for the allowed HTTP methods, specified in the api_view decorator for function based views, includes the GET method but not the HEAD method (actually it is just ['GET']).
This seemed rather odd to me, since the class based views support the HEAD method as soon as GET is supported by just executing the get() function and stripping the content from the response afterwards (at least that's my understanding of how it works).
As soon as one uses api_view(['GET', 'HEAD']) for a function based view, the same thing happens.
But if that works fine, why not just have ['GET', 'HEAD'] be the default value for api_view in the first place?