Profitably has never been the most pressing concern for these growth companies. Amazon went 20 years before turning a consistent profit, so it's not like there is a well-defined upper-limit where profitability is mandatory. Amazon made a trade-off choosing revenue over profitability, and that's what investors want.

Investors care less about actual profits than the ability to prove profits can be generated. Once it's demonstrated/proven that profits can be attained, investors become extremely patient. As long as potential profits keep rising, the enterprise value will rise, and investors will be happy. This is not the Warren Buffett approach, obviously, but that doesn't make it necessarily wrong or invalid. It's consistent within the theory of rational expectations.