Poor old Tony Hoare (algol was mentioned earlier (rightly) as an exemplar of innovation) but Null in a safe memory managed context is a different beast to a true Null reference.
Null appears then as something between a known state and an not quite an exception, it carries different semantics from either, and whilst this could be seen as more complexity, I think the "I just don't know" case in practicality is useful, if harder to reason about.
Your point about the runtime is very true. Partly because of this - error checking is overrated! Yes I said it! We have go code that has been running in a reasonably high scale production environment for over two years and there are `if:...;err != nil` blocks that have never been touched in millions of calls per day, for 2 years. We have redundant services and trap panics in the rpc handlers, the nil becomes very clear and the rest of the system makes good progress. We save lines, save tests, and release a single binary fast. One example of where Go helps us deliver value faster, by being able to choose to ignore exceptions. Many people find this very uncomfortable. I say they are mistaking where the true project risks lie.