IDEs exist to allow teams or entire divisions to hit the ground running with development, with a standard interface that everybody on the same team uses (a huge boon for collaboration), without a lot of time spent configuring or integrating the tools. All the integration is done by the vendor, often better than you can do it; the debugger integration in full-fat Visual Studio is still second to none.

Grooming a personal .emacs or .vimrc is fine if you're working alone, but when you're on a team of professionals working on an application built on a commercial platform, a standard workflow for development is essential and an IDE supplies all the tools, integrations, and conventions to cover the basics of such a standard. Do not underestimate their value.