I don’t think you can short those other things. If someone lends...

I don’t think you can short those other things. If someone lends me a house, I can’t sell it, and if I do, the person who buys it is not entitled to it. The registered owner still owns it.
Even if there’s some clever way to do it that I haven’t thought of, though, people don’t. The consequence is that house prices are far less volatile than share prices.
the reason we have a share market is not to facilitate betting. It’s to provide a way for companies to get investment, that enables them to provide services for the betterment of society. Shorting doesn’t promote that goal at all, it is purely gambling, and in fact it actively serves to encourage people to nobble companies - similar to what happens in other gamble-heavy environments.