> that's pretty indirect and a far cry from "putting the money to productive use."

All finance is indirect. Particularly at small scale.

> Unless you're an early investor or IPO participant

Plenty of IPOs are entirely secondary. And public companies regularly raise money via at-the-market offerings, where a random trader may wind up cutting a cheque to the corporate treasury. (I’ve been a seed investor and IPO investor. My effects on the outcome were rarely singularly meaningful.)

In a large offering, a small IPO investor has about as much direct effect on the outcome as someone buying the pop publicly. In aggregate, however, their actions are meaningful and productive.

Put another way: contrast two economies, one in which most capital is tied up sports gambling (negative-sum game), the other in which it’s in equities (positive-sum long term), one will outperform the other.