Profitability/revenue are not the only metrics that matter to investors. Remember that in order to take out $1M in cash you have to find investors who are willing to pay you $1M for your shares. To investors, metrics like user growth, retention, and engagement also matter (see: Snapchat).
I'm not making any claims as to whether those investors are being smart or foolish.
That seems like a poor example -- from what I've read (and vaguely remember) their revenue is huge (and they could easily be extremely profitable if they so chose) but they're choosing to keep re-investing all of their revenue into expansion, people, tech, etc..
Even if its a requirement of the VC's so that the cap table works out to what they want? i.e. the VC's want 60% of the company at a specific valuation but they can't do that without the founder selling 5% to them.
