Buybacks are functionally accepted as an alternative to dividends, but are not really equivalents. An important distinction is that buybacks not only benefit the shareholders like dividends do, but also benefit the perception of the company's performance by boosting per share financial figures, due to less shares remaining following the buyback. This incentivizes the leadership of a company more towards buybacks, as it not only potentially increases the value of their largely stock based compensation, but it also makes their performance look better.
Off topic, but I wish finance sites published "buyback yield" metric or equivalent (what percentage of total stock value was bought back in last quarter / year / TTM. If buybacks are treated as dividends, investors should be able to assess their returns in a similar way, imho.