Lots of good info here. I have heard people reference the Gig Economy and it's related though I don't think it's quite the same. I guess you could say I took a couple of Gigs in the last few years to shore things up when they weren't going so well.
I disagree about Gig Workers not being as much fun. I think a dynamic and changing workplace can be LOTS of fun. Always new people to meet, network and socialise with. Nothing getting stale or complacent or bored. I could see the Gig Economy really working great in future too. Side Hustle is more about being your own boss and innovating something or producing/providing something that has it's own niche or market. But it's a fast evolving space so that's just my 2 cents! :)