I mostly use the stylus for the Quick Note feature that lets one write and save a note without unlocking the device. Just pull out the stylus and start writing. An independent stylus would not activate such a feature, and in any case an independent stylus is a hassle to always try to keep near the phone, like having all one's keys separate instead of on a keychain.
There are many good reasons to move away from Samsung documnted on HN: https://news.ycombinator.com/item?id=30423815