So occasional +EV situations in Poker and Blackjack for a tiny fraction of the most disciplined players (and only at the direct expense of others) are why non-rich people are allowed to wager their entire life savings at roulette, lottery, and slot machines? And then even more than their net-worth, via lines-of-credit?

But then those same people – no matter how disciplined – must face large (practically insurmountable) paternalistic legal barriers against putting even a few dollars into private investments? Even in domains where they have personal expertise? And where the results can be positive-sum for all involved, rather than strictly zero- or negative sum?

The nonsense is still strong in the dichotomous regulation of gambling and investments. It's almost as if the paternalists want to protect poor people from becoming wealthy!

Roulette with a martingale system has exactly the same expectation as roulette without a martingale system, just a slightly different distribution of returns. Having more money than the house certainly isn't an advantage when you've lost 16 times in a row and they can't honour your next bet...