There are a few reasons some companies prefer buybacks over dividends.
Probably the smallest reason is that buybacks can save investors money on their taxes.
A much bigger reason is that buybacks are viewed as one time events. When a company starts paying a dividend investors often expect that dividend to be paid regularly. If the company chooses to stop paying a dividend or decreases the dividend the share price drops.
Finally, there is executive compensation. Let's say my compensation package let's me buy shares at $100 each. If the share price is currently $110 and the company does a $10 dividend then the share price goes to $100 and my options are worthless. If the company does a stock buyback then the share price goes up and my options are worth more. As CEO which do you push for?