I get what you are saying, but the world is not static. The concept of bookmarks and deep links thus is flawed because they do not/cannot follow changes in the world. Bookmarks need to take a snapshot of the reachable web (this is probably impossible...) or they need to expire after a few months so that the world can change.

I would hate if all nurses manuals had to accept the bookmarks of some book from 1820 just because someone once had a bookmark to the bloodletting section.

As you said, it's not static. You can update the content of pages.

You can also reorganize things and keep old links as 302s.

At a minimum, you should be aware of when you're breaking links and it should be a conscious decision.