The whole point of owning shares is to share in a company’s profits. In simple terms, you make money through dividends or buybacks. Without that, there’s really no reason to own the stock. Sure, prices go up and down, and you can try to profit from that, but if a company never plans to return money to shareholders, there’s nothing real behind the price. Eventually you’d just be holding on until the company fades away or goes bankrupt.

Buybacks are just another way of giving profits back to shareholders—an alternative to dividends with different tax implications. Their purpose isn't to "allow companies to reward executives directly", they are just an alternative way for shareholders to share in the profits.

A company could tie executives compensation to the amount of dividend if it wanted. That might be a good idea.