No one said VC, PE most certainly does invest in startups with exactly that focus on cash flows and leverage. The ones I have experience with tend to look at "older startups" think something like a 7-year-old company that don't really have a hope of a large cash payout but is still viable as a business. It seems to be one transition path for a traditionally VC backed company to resemble a regular small business.

I have personal experience with at least two startups that had undergone that experience and are still around right now.