This is true. However, you have done these fixes after noticing them at runtime. This means that you have solved the null problem for a certain control + data state in code but you don't know where else it might crop up again. In millions of lines of code, this quickly becomes a whack-a-mole.
When you use references in Rust, you statically prove that you cannot have null error in a function for all inputs the function might get if you use Rust style references. This static elimination is helpful. Also you force programmers to distinguish between &T and Option<&T> and Result<&T,E> -- all of which are so common in system's code.
Today it is safe to assume that a byte is 8 bits. Similarly it is safe to assume that the first page in virtual memory is non-readable and non-writable -- why not make use of this fore knowledge ?
> This is related to the drunkard’s search principle (a drunk man looks for his lost keys at night under a lamppost because he can see in that area).
This is a nice example and I do agree in spirit. But then I would offer the following argument: Say, a problem (illegal/bad virtual address) is caused 60% by one culprit (NULL dereference) and 40% by a long tail of culprits (wrong virtual memory address/use after free etc). One can be a purist and say "Hey, using Rust style references" only solves the 60% case, addresses can be bad for so many other reasons ! Or one can pragmatic and try to deal with the 60%.
I cringe every time I see *some_struct in Linux kernel/system code as function argument/return. Does NULL indicate something semantically important ? Do we need to check for NULL in code that consumes this pointer ? All these questions arise every time I see a function signature. Theoretically I need to understand the whole program to truly know whether it is redundant/necessary to check for NULL or not. That is why I like what Rust and Zig do.