It's required if you want to use the build IDE Features to manage your application icion.

Try the following.
1. File | New VCL application 
2. Project  | Options
3. Application Node, Press "Load Icon" and change the icon.
4. File | Save All
5. File | Close All
6. Go to File system delete projectname.res 
7. Reopen Project (Message that projectname.res was recreated)
8. Project | Options and icon is gone.

I don't disagree with having them in an .rc file and compiling them is not a bad practice.

But Delphi by default manages the contents in a res files and hence should not be ignored in a global recommend ignore file.