There are bottlenecks in the Kubernetes architecture that start popping up once you cross about 250-300 Pods per node (the published limit in the K8S docs is actually 100).

This is typically more of an issue when running the cluster directly on large bare-metal nodes because in the cloud or on virtualization the host gets split into more smaller nodes from a K8S perspective.

Obviously this also depends on the characteristics of the workload, if you have a lot of monoliths that you have only barely containerized the Pod per Node limit may not be a concern at all even on bare-metal.