These feature phones didn't have (many) third party apps. Smartphones are all rectangular touch screens, so creating an app that works on different devices doesn't require huge amounts of work (technical and design).
If manufacturers come out with phones that stray too far from the rectangular touchscreen paradigm, the majority of app developers aren't going to customise their app for the phone, unless it's really succesful.
I used to make apps for Smart TVs, when Samsung release their "Sero" rotating TV, supporting portrait orientation AND the orientation changing whilst in the app was too much work, so we just ran it in a letterbox mode.
If manufacturers come out with phones that stray too far from the rectangular touchscreen paradigm, the majority of app developers aren't going to customise their app for the phone, unless it's really succesful.
I used to make apps for Smart TVs, when Samsung release their "Sero" rotating TV, supporting portrait orientation AND the orientation changing whilst in the app was too much work, so we just ran it in a letterbox mode.