I really like my Tab S9 11inch. Why would I buy the Tab S10, if they made the screen a (little wider), because I use my tablet mostly for productivity and a wider screen (when holding it horizontally) is better for productivity, like document viewing and website viewing. Other than that, a brighter screen with some antireflective elements is my second reason to upgrade.
No one is forcing you to upgrade, you can use whatever device you want as long as it works. Consider the fact that there are actually people in this world who don't have a Tab at all or a much older model tablet and would probably want to buy the newest version.
Believe it or not, while Samsung would like for people to upgrade their devices every year, they actually do make products for first time purchasers.
