You may be quite happy in your career. It pays the bills and plays to your interests. You have your hobbies and passions, yes, but they’re fine where they are or are going in the direction you want. Nothing to worry about.
However radical changes can come quickly as we all know. You get laid off. A company moves and you’re not ready to change locations. Your profession starts to contract or alter radically – more radically than you’re ready to face or adjust to. Trust me, I’ve been there – I’ve had many a sudden career change over the years.
So you may be left one day not only without a job, but without many prospects of doing what you’ve been doing. You can’t even rely on relocation because the market has changed so radically that you’re not sure you can count on your old career to work the same way.
You may want to consider hobby-as-career not just as a laudable goal to tap your interests or a “someday” plan, but as a backup career in its entirety. Perhaps for a time – perhaps as a transition that’s more permanent.