Well, it depends on how wealthy you are and the jurisdiction you live in. Loans are not taxable income and if you would have to pay some sort of withholding tax on a dividend (if you would want to borrow against your illiquid shares for example), then it might make sense to take out a personal loan. A bank might also be more keen to give you a loan personally.
But yes, obviously not that common. Random Joe won't be getting these. Random Joe doesn't have $20m in assets either, though.
It's doubly far-fetched to talk about loans to individuals for $20MM. If you're applying for a $20MM loan, you should have an accountant and your accountant should have told you to put this kind of thing in a corporation. You'll still lose a lot but it shouldn't bankrupt you personally.