It's not a coincidence that most people aren't in a position to save enough to live off their capital.
But of course, it's a hedge that has positive expected value even if this scenario does not pan out, so I really don't see the problem here. The stock market still beats all other savings options for long-term (>5 years) investments. No need to see the glass as half empty; we could all be running around gathering nuts and berries and trying not to get eaten by lions.
Why? Because we've heard this one before:
http://www.theguardian.com/business/2008/sep/01/economics
and history has proven it wrong. The increase in productivity happened, but whoops! All the increases went to capital, diluting the pool so that it was just as hard as ever for the working class to jump to the capital class, despite the increased productivity! Funny how that works. Now Marc Andreessen is trotting out the old canard again. Fool me once...
> it's a hedge that has positive expected value even if this scenario does not pan out, so I really don't see the problem here.
I save. You save. Most people that can save do save, because everyone already knows what you're saying. Every gradeschool and every highschool in the US repeatedly burns the lesson of compound interest into the minds of our kids. They even use an interest rate that doesn't take into account inflation or reserve policy so as to exaggerate the effects of saving, if anything.
Some people lack the self-control to save, but they're in the minority. The majority don't save not because they don't know that it's a good thing but because they can't. They're barely scraping by. If the car breaks, there go their savings. If the toilet breaks, there go their savings. Labor these days simply doesn't have the leverage required to carve out a livable chunk of the capital pie, and your suggestion that they have the leverage but not the self-control or knowledge of how compound interest works is patronizing in the extreme.
Also, this 90% of the income-earning population earn more than enough to save considerable portion of what they earn - I earned less than the average before going to grad school, and I still saved >50% of my post-tax income through economically sensible lifestyle choices (shared housing, cheap car and low car usage, home-cooked meals, low consumption on gadgets). This situation is certainly not identical for everyone in the world, but for my five million fellow countrymen, there is vast room for beneficial changes here. Please refrain from accusing me of being patronizing without asking about the background. This is a discussion of a small part of a big issue; this is one idea of what to do for insurance if e.g. you're a programmer and worried about the future prospects of your profession.
You have a point with regards to the "working poor" and other below-median groups, and this is a very serious structural issue. I have never implied that the solution to poverty is to buy stocks.