Image pulls from https not from http even after adding custom registry in Rancher

I have added my private registry server in Rancher custom config. When I try to pull image from that registry it goes into error state. Why? I don’t want to add insecure registry in the host.

Error: Failed to allocate instance [container:1i3039]: Bad instance [container:1i3039] in state [error]: Error response from daemon: Get https://registry_ip:port/v1/_ping: http: server gave HTTP response to HTTPS client

Rancher trying to pull image from https not from http. Why?

What is the need of registry in Rancher if I add insecure registry in Host itself?