Unfortunately too many people subscribe the idea of startups bringing disruptive changes into car transportation because other startups could do the same with entirely different problems. Just because Elon Musk created Paypal it does not mean that he will be able to jump the hoops to get self driving cars on the roads by end of this year. Many people who are intimately familiar with self driving car technologies predict that we need at least 10 years and several innovations before we can seriously consider this as an option.
Of course you're correct that they might not pull it off, but it's not like people are basing any confidence on Musk's Paypal background. Tesla already brought disruptive change to car transportation by making electric cars popular. And Musk brought a third big change by commercializing reusable rockets.
