This user is an extreme example and not the norm for premeds in general, never mind nontrads. Nearly everyone on that forum has had some time out in the real world; some have even put away significant sums of money and can afford to finance much of their med school education out of pocket. The fact that she (not he!) felt the need to even post that thread testifies to her uncomfortable awareness that her debt load is extreme.
It's interesting to see how people make financial decisions in general, not just about student debt. People's debt situation is about much more than choosing postsecondary schools: there often seems to be a notion that "more expensive" means "better" in various arenas of people's lives: cars, vacations, clothes, bottled water, and so on. In other words, the taking on of exorbitant postsecondary school debt is part of a general pattern of spending in many (probably most) people's lives.
Also, when it comes to these kinds of decisions, many people are not willing to walk away when the odds are grossly unfavorable. The truth is that none of us absolutely needs to be a physician. There are many other jobs out there that cater to a love of science, allow you to help people, and would provide a reasonable income without breaking the bank to get there. But somehow, many people get stuck in this headspace that nothing short of being a physician will do, a viewpoint which has always somewhat bemused me. Had I been in the position of the user who started that thread (i.e., already in six figure debt and only accepted to one expensive private school with full loans), I would have simply not gone to medical school: definitely not that year, and possibly not ever. I realize that basing my decision about whether to matriculate in medical school in large part based on financial feasibility would be unacceptable to many people, and I will be the first one to acknowledge that my spending habits make me relatively eccentric. But for me, avoiding that kind of debt matters so much that I would rather have never gone to medical school than to be a physician in her unfortunate position.