There are no /var/lib/kubelet/pod-resources/kubelet.sock in node

I want to know how to enable pod resources gPRC services in node, I have added the flag --feature-gates=KubeletPodResources=true to config file of kubelet and restarted kubelet, but there are still no kubelet.sock in /var/lib/kubelet/pod-resources/.

Cluster information:

Kubernetes version: 1.21.3
Host OS: Ubuntu 18.04.1 LTS x86_64