[thenerdfiles]

Bootstrap isn't a prototyping framework — it's made for production. This fact subsumes the points about (1) testing across browsers, (2) being community-driven (and thus scientific), (3) aesthetic standards, and (4) implementation standards.

Sure you can make your own hammer, and you can even use a non-hammer you find sitting right next to you. But you'll quickly find out that some non-hammer won't accomplish everything you think a hammer ought to accomplish. Bootstrap isn't just an invention/innovation — it is a framework.

Your question honestly is no different from "Why do we need frameworks?" And we just need to stop wasting out time asking these bloated philosophical questions that get us nowhere.

"Why do we need dictionaries?" Well, because if everyone went about their own way, they'd all re-invent the wheel a thousand times over, but we'd never see any cars.