Stock buybacks are shareholder dividends with better tax consequences and less expectations.

For buy-and-hold investors stock buybacks do nothing at all whereas dividends create real income.

For buy and hold investors, stock buybacks do nothing, whereas dividends create real taxable income. Either you take the income, minus taxes, and spend it, or you reinvest it into the stock, again minus taxes.

If you reinvest it into the stock, you've had to pay taxes on the dividend amount, so you've lost vs a buyback.

If you want to spend money and your stocks don't issue dividends, you just have to sell some of your shares. Selling $X of shares will almost always generate less taxable income than receiving $X of dividends as some of it will be a return of capital; so again, if you take $X out of the holdings, you've lost with a dividend vs a buyback and you sold $X.

This is disregarding the definition of buy-and-hold investors. As the name implies, they don't sell stock. Whether or not buy-and-hold is irrational or not is a completely different topic.

Dividends create real income and decrease stock value.

Any time you want that to happen for you, simply press the sell button for some percentage.

Why would you want the company to decide the timing and the percentage for you?

Because dividends are (at least in theory) perpetual.

Selling a couple percent of stock every year or two will work for at least a century before you have to adjust the plan. Something else will come up first.

Can buy-and-hold investors use margin?

Of course, but margin is expensive for retail people.