When Apple introduced its revamped Siri Remote alongside the new Apple TV 4K, there was a common question: why didn't Apple give it the same ultra wideband item tracking technology you find inside AirTags? The company finally has an explanation, although it might not thrill you. Apple VP Tim Twerdahl told MobileSyrup in an interview that there's less need for AirTag-like tracking as it not only stays at home, but is thick enough that it "won't fall in your couch cushions as much." You're less likely to lose it in the first place, in other words.
It wouldn't be surprising if there were other factors as well. UWB support could increase the cost of the remote, for example. It won't likely affect battery life, as AirTags are designed to be passive and wring out up to a year of use even with a standard cell battery. The Siri Remote uses a much higher-capacity lithium pack.
Whatever the reasons, you'll have to find your control the old-fashioned way — or use your iPhone until you stumble across the remote hiding under a pillow.