Because that's literally what buying shares is?[0]: Giving money to the corporation so they can finance future endeavours. Yes, you may not buy shares from them directly but from some other gambler. Still, to be able to sell you shares they need to have given it to Chevron first.

[0] Please correct me if I'm unknowingly bullshitting here!

You'd be giving money to the company if the shares actually came from them. If you're buying on an exchange ... you're exchanging cash for shares with the counterparty almost never ever the company itself. The company is not acting as a market maker on its own stock, for example. The only way the company would benefit is if the purchase increased the ask price so that at the end of the day the price per share was higher.

As you say, someone else has already given Chevron that money. Buying Chevron shares from “some other gambler” does not give Chevron money.