We only know that because we have the benefit of hindsight. But for somebody growing up in the 80s, 90s, and 00s outside of Silicon Valley, I don't think that it would have been seen as low risk when they were deciding what career to pursue.
Think about it. The reason software engineering has been a great profession for the last 3 decades is because an unprecedented number of software engineering jobs have been created in that time span. But most of those jobs didn't exist 3 decades ago (or even just one decade ago).
Somebody who can hack it as a software engineer can probably also hack it as a doctor or a lawyer. Choosing software engineering over law or medicine was definitely taking a risk. You probably had to relocate for a job, whereas jobs in law and medicine exist in most of the country. People were making good money as software engineers, but you couldn't be sure that would continue (I mean, there was the crash in 2000).
Again, not in hindsight. In hindsight, it was a reasonable choice, especially since you avoid huge additional schooling costs. But if you were making that decision 10 or 20 years ago, it was definitely taking a risk vs. the established career paths that law or medicine offer.
I buy the risk argument in theory; anecdotally, friends who are women in tech seem to worry a bit more than friends who are men in tech about long-term career stability. But tech has been low-risk for the last few decades. Even when I was very young I remember being aware that Bill Gates was the richest man in the world, and he did programming, and programming was a thing I could learn. And the number of women in tech has been dropping since approximately the time Bill Gates became the richest man in the world.
I think the risk argument could apply well to high-risk tech career decisions, though, of which there are still quite a few like founding startups. But becoming a rank-and-file software engineer at a big corporation has been a low-risk high-reward career choice for a good while.
See, for instance, this graph of the proportion of CS graduates by gender (from ComputerWorld):
http://core0.staticworld.net/images/idge/imported/article/ct...