This is literally about pockets. Pockets are a fabulous successful technology as they make transportation personal - or rather enable personal transportation. They also define a specific size limit: "It fits in a pocket."
## Typical sizes
The typical size of jeans pockets [as measure by a pudding study](https://pudding.cool/2018/08/pockets/) measures 14.2 cm (5.6 inches) down and 15.24 cm (6 inches) across for women and 23.1 cm (9.1 inches) down and 16.26 cm (6.4 inches) across for men. That also means that on average, the pockets in women’s jeans are 48% shorter and 6.5% narrower than men’s pockets.
## The pocket aggregation rule
Most technologies try to diverge, specializing into separate things. Looking at the living room: A TV, some stereo speakers, a game console, video / HD recorder and so on. Technically a laptop-style device would solve all of that, however if a device is above a certain physical size, they try to diverge into dedicated, separate things.
And while there are efforts to converge, it won't usually succeed above that size. Example: Game consoles trying to "take over the living room", however all the above home entertainment things still exist.
If something fits into a pocket however, it seems to break that rule. The smaller something gets, the more it tries to converge technologies. For example the smartphone converges telephone, messaging, camera, wayfinding and so on. But there are also earlier, low-tech examples - like Swiss army knifes integrating a knife, saw, bottle opener and so on.
As the size and volume of your pocket is limited, there is an incentive to make an item the most valuable - the more use cases it can fulfill, the more likely it will be carried around.