A long time ago, in an industry far far away, there were two competing production models: the assembly line and the master craftsmen.
The master craftsmen hand built each and every machine. Painstakingly ensuring it was beautiful and functional. Each machine was resplendent and tuned to perfection, but it took days to build one.
The assembly line churned hundreds of machines for each one the craftsmen produced. The machines worked and were not too shabby. Sure they were less reliable, less beautiful, and less powerful, but they were also much less expensive.
Soon, the assembly line became the dominant form of manufacture. Producers began to tweak their lines. Some increased the speed. Others added quality control at the end. Still more built machines to do most of the work, seeking consistency and precision.
Eventually, the experiments yielded smaller and smaller results, to the point where running an experiment was often more expensive than the changes it yielded. The companies began to get complacent.
At this time, a young producer decided that instead of waiting to check for quality at the end of the manufacture; they would prevent the part from continuing along the assembly line if its quality was lacking.
Their colleagues were skeptical. "This will never work!" They said. "You're stopping work left and right!" The young producer begged for an opportunity to try their experiment. "Let's try just for one small factory! We'll follow the same rigorous validation process! If it's a failure we can retool the factory to do it the normal way!"
The producers colleagues agreed. A small factory was outfitted to allow anyone to stop the parts from moving through the line. For the first few weeks, it was slow going, with stops every hour.
However, when the line stopped the producer demanded that the factory workers discover why and fix it. Slowly, but surely, stoppages slowed down. Machines were rolling off the line nearly as quickly as the other factories. Even better, very few needed further work after going through quality checks.
After a few months, the factory was outperforming every other factory in it's class. They were building more machines that worked better at a lower cost per unit than any other factory in its class!
The rest, as they say, is history.
The preceding text is a highly simplified explanation of the rise of Toyota and the lean production system which is now buzzwording into meaninglessness in the technology industry. Stop doing lean startups. Start doing learn startups.