Only the newer iPhones show Battery Health. There wasn't a way to track this in the past. While I understand that Apple added this, all it does it make people constantly check and obsess over the fact that their battery health has dropped. Batteries are consumables, and battery health is going to decline with use. You do not need to look at your battery health until you find your battery will not hold a good charge, and then see what it is. As already mentioned, if your battery does not get down to 80% before a year, there is nothing wrong with the battery.