Sleep tracking is not something that most people do in a manner such as step tracking. You can't get up and make yourself sleep more unlike step tracking or calorie counting where you can make an effort to get out after dinner to reach a goal. For those who are doing sleep tracking, I'd imagine it is a short term activity to answer specific questions and adjust patterns. After that, sleep tracking is no longer needed unless conditions change. Otherwise, I feel sorry for those that have to, or simply choose to, monitor their existence THAT much. Diabetics, hemophiliacs and such I understand. Sleep? not so much. And if you do have to monitor sleep, I hope that you are using a purpose built device for the best answers and not some jack of all trades wrist band.
As for the other 99% of reasons to own a watch, Apple or not, the AW works just fine. If you have some arbitrary 3 day minimum for your needs, then the AW is not for you. For myself, I have worn it every day since it was released and never had an issue with the battery being too low when I needed it. YMMV.