Originally "designed" possibly as early as 2000 w/Fukawasa's info bar phone which is now in the MOMA collection uses a particular design aesthetic which now drives a newer version of the phone and which dovetails into the slide interface model which has been patented, licensed and of course now protects a substantial ROI for the companies involved in the commercialization of the design.
The complete article here has an excellent video in Japanese of the InfoBar phone and the UI interface along with the original designs and background. Summary: Design &D leads to proper ROI when combined with IP protection steps and a continuing commitment to new product development rollout.