Comment by jandrewrogers

It comes up quite a lot in things like databases and high-performance data infrastructure generally. The instantaneous resource state is an important input parameter to many types of dynamic optimization. Ideally, you want to run close to the resource limits without exceeding them for maximum throughput and robustness while minimizing tail latencies. Knowing precisely how many resources are available allows the code to opportunistically apply that capacity to workload optimization without risking resource starvation. Some software will also adaptively switch entire strategies based on this information. It is very useful information if you are designing for performance.

If you have no idea how many resources are actually available, you are forced to use conservative strategies to protect the process. Guessing or ignoring resource availability is an excellent way to greatly increase performance variability and reduce throughput.