Expanding on this, if you do all the work on the main thread, you're implementing a cooperative multitasking system, with all of the problems that entails. It

Expanding on this, if you do all the work on the main thread, you're implementing a cooperative multitasking system, with all of the problems that entails. It's surprisingly hard to break up potentially long tasks in an ergonomic way without losing a ton of performance, tracking down a long tail of tasks that block rendering, or both. Having multiple threads of execution is so much better.