This is absolutely true, and the heart of the distinction. If you are happy with a regular job, then definitely go that route. Building weekend apps and such will keep you up-to-date and you'll be highly prized anywhere you go.
However! For many of us, we simply cannot be happy in a regular job. For whatever reason, it rankles and chafes us. For lost souls like this, we need to find a way to monetize and build businesses in order to escape.
I envy people who love their jobs. It seems like a simpler, more satisfying life. It's just never been that way for me.