Why? Several reasons.
Just because something can be done does not mean it should be done. This reason is currently lying dormant, as ours is a technology-fetishizing society and we’re still in the stage of being wowed and dazzled by how smart phones are even possible.
Just because something can be done does not mean it is therefore fashionable and popular. Another one that is currently lying dormant due to technology fetishism, and probably a much more relevant one than the above. Eventually, the fashionable will decide not to carry smart phones. People like movie stars and politicians in high office don’t need them; they have assistants to handle such duties. Jettisoning the phone will be a fashion statement that they are powerful and affluent enough to have such assistants.
This will be much like having a suntan went from being a sign of a common farmer to being a sign of someone privileged enough to have lots of leisure time outside of factories and offices. Even if those without personal assistants still have to carry a phone with them, they will opt for phones that are as small and inobtrusive as possible.
When will this happen? Who knows. It could take another ten or twenty years. I don’t think it will take significantly longer than twenty. That’s a generation, which is long enough for a new generation to see smart phones and obsession over them as yet another dorky adult thing. At that point, the way will be paved for the newest, most fashionable entertainment figures to establish not carrying much personal technology as a fashion statement.
Does my personal bias play any part in my forecasting this? Almost certainly. Yet while I personally want the smart phone era to end, that doesn’t change how the above factors all exist and lie waiting ready to manifest themselves. And personally, I’d want the new trend to happen faster than ten or twenty years, yet I’m not forecasting it will begin soon. So it can’t be written off as purely personal bias.