IME marrying business logic so closely to presentation makes it very hard to change one without the other. Especially relevant for web apps, where you may want to re-use business logic for mobile apps, which becomes very difficult when they're tied to a react component.

Also makes it harder to test. There's a great paper called "Naked Objects" which I'd recommend for anyone doing GUIs, but powerful idea I got from it is make your presentation code so immediately obvious from your business objects that you can practically generate it automatically.