Investing is a good thing, speculation is worse. Investing is usually long term and results on creation of wealth and many positive aspects as side effects.
Yes, the resources might benefit society if they were allocated by AI instead, but this would not be a good thing necessarily as it would stop stimulating humans and our creativity and would inevitably lead to a decline of humanity...
Imagine a star trek world - no need for investing there. It was all about improving wellbeing. It doesn't work in practice in the economy we have though - or the human mindset.