I think the Morlocks do not see themselves as hiding and view themselves more of the types that do not fit into society, and inhabit a area that is far enough away from everyone else put still close enough to serve their needs. Some Morlocks may rather live in the tunnels with others that have similar complications because of their mutant abilities.
Also the Morlocks may appeal to others in the Marvel U that are seeking refuge could lead to potential stories.