Why can not a new project be created by right clicking xcode in the Dock?
Xcode questions.
You mean like Safari new window and Mail compose new message, but not like Pages where there is no offer to start a new document?
Maybe because Safari and Mail are default macOS applications and get more love, and Pages and Xcode are installed case-by-case depending on user need.
Feel free to make feature requests using the bug report link, below right.