The Apple TV comes with a remote, but like all remotes, it's slippery and easy to lose in the cushions of your sofa.
Meanwhile, owning an Apple Watch means you'll never lose your remote because it's literally attached to your wrist. It does not have Siri – of course, the only time Siri is useful, it's not available – but you can still use your Apple Watch to play, pause, scroll and navigate the menus.
To enable this feature, simply open the Remote app on your watch. It looks like a blue play button. I keep the Remote app in my Dock, which you call by pressing the side button on the watch, for quick access.