Alphabet just announced a 25 billion dollar stock buyback.

Amazon and Facebook are growth stocks so investors don't mind them holding some cash to make investments, fund acquisitions and what not (which is what everyone here seems to want). However, they'll both probably hit a 100 billion dollars in cash in the next 5 years and I would expect dividends/buybacks to follow soon after as that is more cash than anyone reasonably needs.

They don't (currently) issue dividends because the expectation is they will buy back their stock or will issue dividends in the future.

If a company never issued dividends and never bought back their own stock, then there would be no reason for investors to buy stocks in the first place. Most investors don't invest out of the goodness of their hearts, they invest to get a return on capital.

Do you think that all of those people are insane? Surely you must realize that shares of non-dividend paying companies are valuable because they are expected to eventually begin paying dividends.