Why dose the k8s add only slave nodes to Octavia as the member of pool?

Hi. Now I’m testing LoadBalancer Service with Octavia. Today I found that OpenStack plugin of k8s adds only slave nodes (not master node) to Octavia as the member of pool.

Is there a reason for this?? I know that a master node can act service load balaner such as a slave node. So I think that the best way is providing member option such as ALL, Master, Slave…
Is there a history or reason?? Thanks.