Ask HN: why don't startups/high growth companies raise debt rather than equity?

For the earliest stage companies, it's pretty obvious why they don't: they can't. But it seems like a lot of companies with great traction (~$1 MM in revenue), recurring revenue (subscription to content, products or software) and need are out there raising VC money in what amounts to equity (I'm counting convertible debt here, too). Why don't they try to use forward receivables to raise debt either between or in place of an equity round, which even at a high interest rate, is cheaper than equity?