If earnings are the main point of your life, that makes perfect sense.

I bet that a substantial majority of people's long term goals involve money to some extent.

Want to live in a van and surf all day? You do actually need money for that, particularly if you want to do it indefinitely.

Sure, resource potential is important. But putting all of your eggs in one basket can push you into a corner, especially in the sense of -feeling- cornered. Options, even if they exist primarily in theory, are a force multiplier.

For example;

If you have a “good” job, but it is trending toward a flat trajectory, and you have a set of skills that requires a complex set of circumstances to be employed, it may be too risky to move to a new location simply because the downside is so severe. It can be a 1:4 bet paying 10:1 odds, a bet you definitely should take, but if losing means your family doesn’t eat, you can’t take the risk.

If you know you can find a way to get by even with day labor if things go badly until you can stabilize your situation, you can take those beneficial risks.

It’s a matter of being prepared to roll with the inevitable punches, and being able to make decisions based on the knowledge of that readiness. Being less fragile, even antifragile.

Earnings aren't the main point, but they're a necessary point for everything else that does matter.

Sure, and optimizing earning potential along with tactical flexibility is arguably the best way to maximize that potential. Having a trade as a backup skill gives you tactical maneuverability that allows you to be a more effective negotiator and to take beneficial risks. Negotiating power alone is worth any costs.