I *think* it's just because it's a major hospital in East London, it happens to be packed. Then, so are other areas of London. Having said that, they closed about three hospitals and then opened that one, so it's going to be in demand. My local (little) hospital is actually far, far nicer. About 10x nicer. The area itself is middle to upper class, and it's surrounded by trees.
I wouldn't want to go to Basildon hospital. Oh, here's a funny story: When my sister went for maternity aftercare there, they said they had mothers enquiring about whether they could puree McDonalds food for their babies.
Perhaps that's not such a bad idea.