Why is the RBAC of traefik-ingress-controller restricted to namespace default?

IDK if I got it right but when reading your RBAC for the Traefik CRD it seems that the ServiceAccount role is limited to the default namespace, right? And if yes, why?

kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1beta1
  name: traefik-ingress-controller
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: traefik-ingress-controller
  - kind: ServiceAccount
    name: traefik-ingress-controller
    namespace: default