The companies I mentioned are all alike in that they have nearly zero marginal cost of production; zero cost of distribution (they grew virally); early markets that could be reached with a product built only by the founders; and a lack of competition. Together, that means low costs and high profits, which means they didn't need to take much investment (Facebook is an exception, but they took it all on very advantageous terms), which means they had investors begging them to invest rather than them begging investors.

The ones that got diluted did so for different reasons. My understanding of PayPal is that it's because of the number of pivots and corporate restructurings they needed to do before finding product/market fit; they started as 2 separate companies (X.com and Confinity) in 1996, and didn't really take off until 1999. My understanding of Box is that they need a very expensive enterprise sales process to generate revenue - they don't get the viral growth of say Hotmail or even DropBox. Lyft got in a price war with Uber, and spent billions on ride subsidies to generate consumer demand and ensure they were price competitive.