The argument that executives should develop side projects and supplementary income streams isn't wrong about the value of skill-building or career optionality—it's incomplete in a way that reveals something about who gets to benefit from good advice.
Someone working a demanding full-time role takes on a teaching gig, a consulting project, a freelance engagement and learns things the primary job never taught them, builds a network outside the organization, gains leverage—yet the narrative treats this as available to anyone with ambition and evening hours when it simply isn't.
Consider what actually has to be true for this to work: you need enough financial stability that a failed side project costs you nothing, enough energy at day's end that unpaid labor doesn't collapse into sleep, professional credibility that someone will hire you without lengthy vetting. A schedule flexible enough to attend evening seminars without your primary employer noticing or objecting. Most crucially, you need the unstated permission—the cultural assumption—that this is normal and acceptable for someone like you.
A vice president at a bank teaching an evening marketing course looks like ambition and growth. A bank teller doing the same looks like distraction—and the difference isn't the actual time commitment or learning outcome. It's the invisible assumption baked into the first scenario: this person has margin, room to give, capacity to absorb risk. The second person, statistically, is working another job out of necessity, not development. The advice lands differently when you're not sure you can afford to fail at it.
The article assumes discretionary hours and discretionary money — the two things that most full-time work is designed to extract.
If you're someone with enough cushion to try this—to take on the evening course, the consulting project, the paid teaching gig—it works. You'll learn things and meet people who matter and build optionality, so do it, because the data on skill development and career resilience is solid. But notice the real tension: it isn't between your full-time job and your side project—it's between the people who have enough discretionary time and money to treat risk as a learning opportunity and the people who can't afford to find out what they're capable of until the financial pressure eases. Statistically takes decades.