Sure, but that's a bit like arguing that you don't need 'scope' for your variables and you can just prepend the function name (or multiple nested function names). Or that you don't need modules but can just put all your code in one file.

At the very least support of nesting is a huge convenience, but in practice I've also found that it saves me from all sorts mistakes, whether it's because I'm being stupid, or refactoring things.

That said, overusing nested selectors can be a problem too. I generally try to limit myself to two levels of nesting (component -> element), and then a third for pseudo-classes (:hover, :selected, etc.) and pseudo-elements (:before, etc.).