It's not often discussed that Microsoft, Amazon, and other 'very cool' tech companies still practice this 80s firing the bottom 10% bull.. It has nothing with being a low performer, but everything to do with culling jobs indiscriminately and creating an in/out culture. Managers are forced to place employees into bottom performance slots, sometimes arbitrarily, so that teams/groups/departments fit the bell curve nicely. Then, people get fired, bonuses go out, and everything is peachy at the end of the fiscal yesr.
Let that stew for a few years and these behemoths are factories of pet projects and crunch culture. Your long-timers are either golden performers who've seen massive churn and project turbulance OR they're climbers, willing to step on top of anyone or burn any project to climb the ladder or at least keep their spots.