The UD is inherently not very beginner friendly and the lack of CR indicators and even more importantly the area markers really add to the confusion and making it harder to find one's way around.
While Tsidkenu has a point with it promoting some guide RP, I think it actually promotes difficulties for newer players in this already hostile environment.
Even those that are experienced on the surface that now want to play in the UD might shy away from doing so because it's just less comfortable than in the land of unicorns and sugar (surface)