Do most organizations create and maintain a network diagram?

Do most organizations create and maintain a network diagram?

I'm currently studying for my CCNA and from the troubleshooting I've been doing so far I notice that having a network diagram helps me visualize the expected path that the data will travel. Without a network diagram and knowing exactly how the network is physically inter-connected I'd probably be stumped by the simplest network problems.

If I get a job as a network engineer is it likely that the organization will have a network diagram? Also does the CCNA exam usually provide a diagram for troubleshooting questions?