An Integrated Development Environment as the name suggests integrates all of the tools in a developer's environment: editor, compiler, debugger, source control, servers. An editor is just one part of that.
vscode is intended to be a compiler/debugger/etc. It can already debug node/mono apps. Checkout dnx, .NET Core, and Roslyn. Soon, Visual Studio will not be needed for pure c# applications, except traditional MSBuild/csprojs and C++.