C is a simple language, C++ is not. For many people, C++ is simply too complicated to fully master, see http://en.wikipedia.org/wiki/C%2B%2B#Criticism.
Because of the complexity, different programmers usually only master different subsets of the language. It makes reading other people's code painful.
The complexity, pitfalls of the language add too much distraction, and sometimes hurt productivity. Instead of focus on the job itself, I often found myself fighting with the language itself. Java/python are more productive alternatives.
Debugging a broken C code is usually much more straightforward than debugging a broken C++ code.
Unlike Java/C#, the C++ standard library achieves little beyond the scope of the C standard library.
Some famous programmers like Linus Torvalds (Linux) and Richard Stallman (Emacs) dislike C++.
