These are all different options on the sliding scale of portability vs usability/screen size. Folding phones lie between a slab phone and tablets on this scale. I’d say slab phones > folding phones > tablets > laptops > desktops etc… You also of course have further subdivisions such as the iPad mini vs the iPad.
This is like the people saying, at the launch of the iPad, that tablets would fail because laptops exist.
Then the plants would have no water and die.