One of the consequences (although arguably not the primary motivation) of DRY is that you tend to end up with chunks of complex code expressed once, with simpler code referencing it throughout the codebase. I can't speak for anyone else, but I consider it a win if I can reduce repetition and tuck it away in some framework or initialisation code. Having a single accessor definition for a commonly used accessor makes me happy - and the new Object class code can be tested to hell and back. The upshot is more beautiful, readable code.

Yes, you can embed loops in it and compose lots of small repeated JSX snippets, but that almost never happens in practice because mixing the turing complete of javascript with the markup of HTML eliminates the readability of JSX so that it is actually harder to parse than a solution like hyperscript (the syntactical approach taken by virtual-dom).