It's very important features for users, please everyone tell this to samsung each and every times. We have to make it possible by ourselves to give feedback in a tons for our features.
Secure Folder requires Knox which is a both hardware & software based security so your phone should have that hardware so that Samsung can provide Secure Folder through software update.
Besides Secure Folder comes preloaded in the devices that has hardware level Knox. You need not to download it separately.
