Of course it adds to the wider economy. These funds make money, they're taxed. Quite simple really. I also know of a couple of systematic funds in London that give very generously to various charities.
They're taxed on fantasy profits, and utterly distort the economy in the process. When there's an upward shift in the value of a share, nothing new is created, made or otherwise value-added all that's changed is a number. That number is then converted into "real" cash. Which is fine to a point, because markets themselves do add a certain amount of value in the ability to liquidate assets, invest and transfer wealth, etc. - but the current state of affairs results in market trading being profitable out of all proportion to its actual value to the economy and, worse, badly distorts the incentives so that a small number of not actually that skilled or talented receive inordinate wealth. That wealth then distorts the local housing markets, etc.