This pack is very nice... but it's just a "pack", it's not a "battery".
This is a "pack" of cells:
Also this is just a "pack" of cells:
This is a "battery":
The difference is made by these:
The point is: the "can" of a lithium cell is also its negative pole; it's wrapped with a thin plastic foil; if multiple cells connected together in parallel or series (like in a battery) touch one to the other, only this thin foil prevents short circuits. If it's a stationary battery, that's all you need.
But for road applications (bicycles, motorcycles, cars,...) you must take into account vibrations: the wrapping of two cells in close contact slowly wears out at each vibration; wears out, wears out... until the underlying alluminum bodies (i.e. electrodes) connect together, in an unpredictable position of your battery; and you don't want an unpredictable connection between cells in a battery.
The above shown "plastic things" are called "cells holder", but they also act as "cells separator", and they're a mandatory part in any road-battery (if you want a safe battery).
Of course they increase volume, weight and complexity... but also safety.
Note: if close cells inside a box touch one to the other until insulating wrapping wears out, nothing happens, because cells are not connected together.