It's not that failure is eliminated, but you can run a business with almost no risk or capital exposure. If that business fails, you walk away with no damage done.
You have no capital exposure if either you (a) work full time and your living expenses are $0 e.g. parent's basement, or (b) you have a job to pay your living expenses and work on your business in your spare time and value your spare time at $0.
Really, what type of companies are those? I've always seen the comment of, "there are so many more ways of making money than X" without the actual proposition of said companies. Hell, even Sam Altman said it in the Stanford Start-up class, but didn't give any examples.
Right. If you bill one hour and don't have to issue a refund, you're in the green. Nearly impossible to mess up. Harder to mess up than being an Uber driver with lower capital requirements.