This is a good point. Null pointers are the billion-dollar mistake, but the real billion-dollar mistake is having "zero values" in your language. In addition to the problems with null pointers, zero values make loose constructor semantics like C# and Java tempting, where objects can exist in a not-fully-initialized state, leading to lots of room for confusing bugs. Without zero values to fall back on as a crutch, the language design is forced to tighten that up so that objects are either completely initialized or completely uninitialized, like in ML or Rust†, which is a much cleaner semantics. (The funny thing is, Go has the tools to get rid of zero values by virtue of not having constructors, but it chose not to use them for that!)

† Strictly speaking, objects can be partially initialized and partially uninitialized in Rust, but this is harmless as the borrow checker statically ensures that uninitialized fields of objects are never accessed.