[perl4ever]

Not everyone owning a given company has a risk/reward preference that matches some hare-brained acquisition.

However, the S&P 500 is approximately the same as the stock market, and so I think it's arguable that "everyone" together does have about the same risk/reward preference.

Buybacks, even if better in the best of all possible worlds, make it difficult to change your mind, whereas an index fund could simply be sold, rather than having to issue more stock. It seems like a lower-friction alternative to accomplish something economically similar.