Stocks are not completely nondeterministic games of chance, which is why most people who hold properly diversified stock portfolios have seen long-term growth instead of loss. That's probably why people don't call it gambling.
> Stocks are not completely nondeterministic games of chance
That's a bit of a straw man, as no one claimed they are. "Gambling" is often not a nondeterministic game of chance, either. For example, when I go to a casino and play poker, I'm still gambling, even though there's plenty of determinism and strategy to go along with the elements of chance.