That's really 2 questions I think.
Question 1. What are the certs focused for?
The CCNP is a Business networking professional. They manage the internal access and intra site routing of a business. Typical day to day responsibilities would include network monitoring, the design and build of a new site and resolving connectivity problems for users and sites. They focuses on Switching, Intra company routing and administering other network services like fireballs, wireless and service appliances.
The CCIP is a Provider based networking concentration. They mainly deal with larger metropolitan areas working on connectivity issues with both business and residential customers. They specialize in monitoring and managing data flow efficiency with QoS, and Service SLA guarantees. Focuses on Routing and routers both large and small. QoS and traffic flow management and monitoring.
CCDP's are typically consulting engineers or work for larger businesses managing the overall design and deployment of their clients business needs. They design and test possible network configurations to ensure those needs are met. They focus on finding the right combination of equipment and the tools to solve a customers problems.
Question 2. What job do people with theses certifications do? That is an entirely different matter. I have certifications from MS, Novell and Cisco and have always been a server guy, put I am currently working as a Voice Engineer. I have a friend who is a CCIE R&S and he owns a flower shop. And I bet we all know someone who has a cert or two but could not de-bug a windshield without help.
The important thing is to have fun and enjoy both what you are studying and what you do. The certifications open doors and provide insight into the technology. You do the work and make the difference. I have never taken a class where I did not learn something to help my career even when it was things I did for fun.