If true it makes them terrible investments, because their future income streams can't be estimated with any accuracy, so they cannot be valued.
But in reality it's not totally true. SnapChat and (probably) Instagram have huge installed bases, but haven't yet figured out how to monetize them. They aren't businesses or investments, they have no strategy other than just pure speculation.
But Uber provides a service connecting riders with drivers that costs pennies per ride to deliver and earns dollars per ride in revenues. If you know how much Uber is spending to build out markets, and on unneeded distractions like UberEats and self driving cars, you can estimate the value of their core business. Uber's strategy has never changed, they've just obfuscated it.
I think that with new companies, like Snapchat, Instagram, or even Uber, changing strategies on a monthly basis has become somewhat of a requirement.