It's really hard to find actual range information for the air tags.Early reports all say about 30', which is typical for bluetooth. But it turns out that the range could be out to about 300 feet if they use bluetooth 5. If so that makes a big difference in their usability for rocket tracking.
At most launches the rockets typically recover within the same general area. Given the prevalence of iPhones, it seems reasonable to expect that someone looking for another rocket would pass within 100-300' of one that flew a fairly similar flight profile and their iPhone would pick up the signal. I wouldn't use something like an air tag for a rocket going to 1,000's of feet, but for a smaller model rocket that might land in heavy grass, weeds, or a crop cover, it could very well be very useful. But if the actual range is only 30', then probably not so much.
My guess is eventually enough flyers will try it that we'll know how useful they are in real life. In terms of cost, other than a simple noisemaker, they are about as cheap as they get.
Tony