contacts: GUI concept

I find the groups and view functionality under iOS rather complicated. Why is the GUI concept different from how I can browse through folders such as in Mail for example. I don't understand why Apple is using another GUI concept for pretty much the same purpose?

In iOS Mail I can browse through different folders back and forth.

In iOS Contacts I can only enable groups but the user has absolutely no clue which contact belongs to which group.

THANK you!