What franchises represent, to me, is the new search for continuity. The world is changing faster, relationships are getting more tenuous. Moving around, finding new friends, new places to hang out and eat and drink and be merry; All these things have been enabled by the internet and the sharing economy. I moved to a new town about 3 months ago, I eat out every night and I've eaten at precisely two places twice: A korean joint I like because it's named for Psy's masterpiece, and an indian place a former coworker recommended. The rest of the time, I've been trying new things, searching for the 'perfect' meal, never satisfied. In this search for novelty, something has been lost.
There's a reason why you see so many tumblr handles of the form 'harrypotterlover21' and 'twilightfan32'. People identify with these stories and universes, and find their sense of connection and emotional stability with them. It's no longer specific people that you have a connection with, but a grouping based on a shared interest; perhaps one that belies a mindset?
It ties into, as well, the current trend of TV shows to be long-form entertainment. We want to see characters grow and establish themselves. 1 1/2 hours isn't long enough. 3 hours rarely is. Franchises allow stories to be told iteratively. That's a good thing for movies and art. There's nothing special about the traditional runtime for a film that makes it more artistic; that's just how long humans are willing to sit down and focus on one thing at a time.