Companies can be useless and generate revenue, a gambling company is a good example. I believe it is possible to define their utility without relying on revenue. Talking about the stock market itself however, the utility of stock is to generate revenue for the owner. That is very much like gambling when relying on stock price volatility or growth and it is unlike gambling when relying on the underlying business to generate revenue.

The main difference being that gambling will not reliably provide returns, while stock will provide a somewhat stable revenue.

I do see differences. Besides, gambling is very often not about making money.