Apple in the new iOS style is using natural textures everywhere — leather, wood, fabric looks on the calendar, contact list, reminders, etc etc.
In the past the UIs were all brushed metals (aluminum? the “OS X” look) and before that translucent glass/plastic (“Aqua”).
Maaaybe, these guys choose texture themes to go with what the display technology allows.
The textures look great on iPhone and iPad displays.
But see how they translate to your crappy laptop LCD screen in the similarly-themed icloud.com –> they look bad IMHO