The GoF book is one pattern language among many. They were concerned with OO design that is used in a class of programs they had experience with -- basically G

The GoF book is one pattern language among many. They were concerned with OO design that is used in a class of programs they had experience with -- basically GUI programs with runtime extension, and with a bias towards programs that create documents/digital media. There are many other pattern languages -- I could imagine one for web development that had your three examples and others.