The S&P has had a positive price change 23 of the last 30 years, yet the average expectations of these "adults" has been that more than 60% expect a decline pretty much every year.

Yes. The current level of optimism as shown is unprecedented in this century; and especially surprising, I would have thought, given that the winner of the recent election consistently portrayed the economy as doing poorly. But maybe that's what has moved the needle: people who believed what they were told about the economy's miseries now take heart that it will recover its health.

What's most striking, though, is the point you make: most people don't know that the stock market goes up most years. Gregg Easterbrook wrote an article long ago on why economic news is always bad, and he was certainly on to something. If unemployment falls, can inflation be far behind? A strong dollar is bad for exporters. A weak dollar is bad for consumers. And a rising market means the next crash is closer than ever!

I think people whose acquaintance with investing consists of random bits of day to day journalism could easily conclude it's a sucker's game.

Baltassar