The problem is it's very easy to write non-performant JS code if you're adding/removing/modifying lots of DOM elements, and attempting to do it performantly by-hand tends to lead to a lot of bugs. VDOM isn't performant in the sense that it modifies the DOM faster but in the sense that it allows you to write code that wouldn't be performant and have it execute efficiently. In React you worry about your data flow and component structure without needing to worry about DOM performance.