Eventually you end up with registers that probably allow for 2^N values. But the point is not thinking about the machine executing the instructions, but the construction on top of it that has a safer design.

Seeking performance we've been very prone to avoid abstractions and over and over again have shown why we need the safe abstractions.

Rust is a significantly higher level language than C, but it can be used it almost all environments where C is used; provided there's a supported compiler target for it. In (safe) Rust, null is basically a guaranteed compiler optimization. Optional / nullable values are represented via Option<T>, which is a sum type of Some(T) and None. When a reference or other pointer-like value (e.g. Box<T>, an owned heap allocation) is wrapped in Option, the compiler can use the invalid bit patterns of T (such as null) to represent the None variant. This is called niche optimization.

So yes, it's nulls underneath, but the developer never has to think about them.