One missed paycheck can turn into multiple missed paychecks, which can fuck over even the people with a rainy day fund.
I'm a tech gal in SF, but there was a period of ~6 months or so where I had back to back to back upper respiratory infections from hell and I was so fatigued and ill that I wasn't taking up any new contracts. Lucky for me I'm my own boss, and lucky for me I'm a cheapskate with a big rainy day fund. Not that many employers would put up with someone not working for 6 months at a time. "Doing something wrong" doesn't just mean "incompetent developer" or "person spending beyond their means". It could be something as simple as me being out of commission this entire past week because sinusitis (seriously, fuck these infections) plus nausea/period cramps. It could be something as awful as being terminally ill.
That's just myself too... my husband and I just started trying for kids, so that's an additional layer of responsibility we're preparing ourselves for. Then I don't know what might happen to either of our parents, just in case. The list goes on. One paycheck can absolutely make a difference, and not just of the "you must be stupid" variety.
I agree with you, but many people are doing something wrong. I've known plenty of people in tech who do not seem to be able to live below their means. I've had coworkers/managers/friends look at me like I had an extra head when I balk at the cost of things that don't even seem to register for them, especially when I mention I save 40-50% of my net income (and my pay isn't particularly impressive by silicon valley standards).
It's easy to save with no debt, no family and an income that is even 50% of the typical entry-level SV income. Most--as in the majority--of people who "work in tech" especially of they're younger than 40 had to take on significant student loan debt to get degrees, certifications and what have you to get those jobs. Your savings rate is extraordinarily unusual, and it doesn't necessarily mean you're smarter about money matters, or that everybody else is dumb about them.
