It's always been this way
But the elephant in the corner of the room that everyone likes to ignore is this: People with these "side jobs" are often working smarter, not harder. For example, say you want to start a side business selling something online? You may have to burn a few of those precious weekends working on the setup -- but once the e-commerce site is running, it sells to visitors 24 hours/7 days without you having to do much with it. Your role is probably only going to be in the packing/shipping of products ordered, and handling returns as needed. Granted, that can take some time, but you get to choose when you do it and for how long. You could box up a few items right before bed, perhaps? Or knock some of it out while you're watching some show on TV at night, relaxing. If it does well enough? Now you can afford to pay some teenager to do the hands-on stuff for you, making the operation completely hands-off.
And same kind of thing with people who really do find a way to make their second job a sub-set of their hobby. I know a guy in town, for example, who is really into history. Since he was interested in digging up everything he could find about local history in our city anyway, he decided to start compiling it into books. He's got 3 of them out now that he sells via Facebook and occasionally at a local flea market table, or in other people's shops. He was going to hang onto all of those notes and photos and copies of historical documents anyway