This is very odd and I just noticed this for the first time, but it seems, apple is not allowing ratings from customers for its own Postcast.app.
The entire section "Ratings and reviews" is absent for the podcast app: https://itunes.apple.com/app/podcasts/id525463029
Other apps do have ratings and reviews. Below two screenshots: 1. showing podcasts app without the section in question and 2. showing soundcloud (as example) with the "Ratings and review" section.
I find this disturbing and unsettling. Apple does not allow ratings for it's own software or what? Can someone enlighten me about what's happening here?