Nolan Bushnell's article highlights the battle
Start-ups are by their nature messy. Management will make mistakes, markets will be slower to take shape than you anticipated, and the technology will be buggy. In a bootstrapped company, you can survive because your expenses are low and you are accountable to no one but yourself. But in a funded company, you must demonstrate to your investors that you are making progress even as cash flow continues to be negative for a much longer time, requiring added rounds of investment.
