And they wont because they cant figure out how to have it all at the same time:

• move out of the way of the big screen for watching video
• be easy enough to switch to and tactile enough to be worth using it more often than the touch screen
• doesnt make the phone too thick
• doesn’t make the phone too long
• doesn’t make the phone so complicated mechanically that it falls apart in a year because they refuse to build it with better parts to last no matter the situation

You can do some of these but not all of them at once.

These will continue to be gimmicks and not mainstream.