There are many, many, many cases where communication is not possible because who is working on the code now didn't exist when it was written (unless you want to

There are many, many, many cases where communication is not possible because who is working on the code now didn't exist when it was written (unless you want to take the time to document out all of your CSS and hope that everyone who touches it follows that documentation exactly). A new team taking over, a new agency updating a website for a client that was made by another agency, a new developer being brought on, etc.