When your business explicitly depends on quality, you obsess about it. You ask interview questions about it. You develop new processes and tools and culture to support it.
Self-driving car companies pay Scale to take thousands of images and draw boxes around all the pedestrians. If they miss one, then the car might run on software that does the same. Down the line, everybody gets hurt.
So Scale works very hard to draw good boxes. To make extra sure that they don’t mislabel any pedestrians.
This makes them “the best.” Customers like “the best.”