not everyone responds to a perceived social ill by thinking "maybe I should gamble"
It’s an incentive for people to root out corruption and graft. If you truly believe that SpaceX is a big scam and it’s not actually worth enough to be in the S&P 500, then taking a short position not only will net you a bundle of cash, it will do the public a service by helping to expose a fraud and prevent future companies from doing the same thing.
That societal benefit is mostly worthless to investors.
Investors need to capture a good return (risk adjusted) to have any incentive to expose frauds or scams.