Tenure helps eliminate bias and financial influence from research. Research that people like Elon Musk rely on in order to make money.
Risk isn't really a factor. It's just really hard work with no immediate returns.
But you need people like Musk too, who apply that knowledge. The research makes electric cars possible, but people like Musk put them on the road and in space. Two different models necessary to society.
Why is tenure so important?
You're surrounded by 20 year old blue haired angsty people who aren't dealing with their hormones. Tenure makes those profs not a target.
I wouldn't call them risk averse. You get paid peanuts and treated like crap for years in the hope that you'll find a research path that generates funding. It's a lot less risky to get a private sector job and make money.
As far as Elon Musk versus professors, it's a different type of risk. I knew somebody who sacrificed a lot of potential money for years of his life so he could try an contribute to research for a specific medical condition. He was brilliant and I'm sure he could have made 4X the salary in a tech job.