Why is a billionaire attempting to reverse ageing by injecting the ‘young blood’ of his 17-year-old son?

Like many celebrities and entrepreneurs, 45-year-old US tech billionaire Bryan Johnson is trying to reverse the ageing process.
Spending an average of $3 million a year on an anti-ageing regimen, Johnson claims he now ages slower than some children.
He explains: “The pace my body accumulates ageing damage is less than the average 10-year-old.”
Many of Johnson’s age-reversal methods are questionable, involve dodgy science, and have known side effects.