There's another couple of good reasons for the combo.

First, if the 9-5 suddenly disappears, you have something to ease the blow.

Second, you're not likely to ever get real wealth from a 9-5 (waves hands at inflation, cost of living, and stagnant wages). BUT it might keep you going long enough to build a bestselling course/book/screenplay from your side hustle, and next thing you know the 9-5 is the quaint thing.

Long odds, sure. But better than the lottery...

Great article, and congrats on the 9-5 from a fellow 9-5er.