[rkangel]

It's difficult to answer this question with 'one main reason'. Rust is what you get if you build a language that is intended to operate in the same space as C and C++, but benefits from the last 30 years of advances in programming languages.

Some things that are better as a result of things that are hard to do right in C++:

* Compiler monitors ownership of memory

* Compiler monitors ownership across threads

* Generics aren't handled as templates, and you can explicitly describe support using things like * trait bounds

* Macros are useful but need to operate on something more like the AST rather than text tokens

* A richer type system can help you express much more in the types (Rust enums)