A startup in general cannot afford to get the best people in the field, unless it's some super sexy bleeding edge tech (which is very rare). So, you are lucky f

A startup in general cannot afford to get the best people in the field, unless it's some super sexy bleeding edge tech (which is very rare). So, you are lucky for your first 10 engineers to have one great one, and hopefully no awful ones. And you cobble a codebase together, and the overriding goal is that it isn't totally broken all the time. Growth first, maintainability last. That's the incentive in a startup. Unfortunately, in larger companies most managers don't reward improving the codebase unless you are on the platform side, just new shiny new features. Nobody will love you for saying this quarter I removed 2000 lines of shitty code.