Is this accurate?
I was reading reviews of the Game Boy Micro a few years ago (written when the Game Boy Micro was released in the early 2000s). Many described the product as "as small as a cell phone". I found this funny—it's significantly smaller than smartphones today—including the original iPhone, by the way, which wasn't small when it came out.
I'd say the trend has been towards larger phones as we've begun to use them more and more. If you use something most of your day, you don't mind so much if takes up more pocket space.
You may be right in terms of thickness, although I think it's too early to call that a trend.
https://i.pinimg.com/originals/f7/35/1d/f7351d374bbbb01da339...
Blackberries were never that small, and weren't trending downwards in a significant way.
Probably in the early 2000's when small equaled good.
My wife had an LG phone that was so small it fit in the palm of my hand with my fingers closed. Sony sold a phone so small that it had a boom mic that swung down a couple of inches to pick up your voice.
I had a SonyEricsson t68i that was 4" x 1¾" x ¾": https://www.gsmarena.com/sony_ericsson_t68i-325.php
I currently own a phone so small that it doesn't even have a keyboard[0]. When they get the thing to fit in my ear, then I'll start to worry that they're getting too small.
I'm being just a bit facetious, but in seriousness if voice-controlled AI can improve a bit, size might cease to be an issue.
[0] Apple Watch, and the only thing keeping from just ditching the phone is a. battery life b. Apple's use case they designed for is not "ditch the phone".