The Unity editor gives you compiler errors and warnings in its console window. Why shouldn’t it give you these warnings as well?

The Unity editor also has lots of features that IDE’s have already, including a profiler, ability to inspect the world hierarchy, inspectors for components on that hierarchy, and ability to pause and restart execution.

How about a code editor? All IDEs have code editors, you know. Unity doesn't. Because, again, it's not an IDE.