Isn't it to some degree? My understanding was with index funds was that the index is required to be backed by some in-kind holding of the component index products by whomever minted the index share. If more people buy the index then more of those in-kind backing products must be held e.g. as collateral. If you're REQUIRED to buy this stock because of your index/etf positions, necessarily the demand goes up, and necessarily the price goes up too. Companies _definitely_ materially benefit from stock price increases.