True. I've been wondering why mainstream films are getting longer, too. 2-2.5 hours has become the norm.
I don't think those films you mention are actually mainstream hollywood productions.
In which case, the ~60 minute length is not surprising: it has been the case for lots of alternative films over the decades, and it's the very cutoff point lots of film festivals use to separate the two categories (though the Academy uses 40 minutes for that purpose).
Compare "Back to the Future" (any one) with whatever new movie in this genre you can remember.
On the other hand, it's also only 100 min. long, so it doesn't exactly fit with trend of longer movies.