If it's true that self-driving is likely to be developed in the next 10 years than Tesla and Uber are good investments, because there's a reasonable chance of a world-changing, market-monopolising product making your investment incredibly profitable.
If self-driving is unlikely in the near-term then Tesla and Uber are not so attractive - you're looking at investing in an overvalued electric car manufacturer with limited production and a money-pit taxi operator, respectively. If a moon-shot innovation like self-driving is still likely in the next 25 years then on the other hand there's not a whole lot of reason to believe that these companies are the one's that will get to capitalise on it, rather than the established (cheaper) manufacturers or some new upstart. There are far safer investments out there.
All that's happened here is that people have lost faith that these companies are likely enough to develop a world-changing technology to justify their recent high stock prices.
Yeah but this is colloquial speech, the probabilities are there just implicit because it would be exhausting to make this explicit in everyday speech.