Don't have to. But they can.
See also question already asked on 20 July 2016:
https://www.digitec.ch/de...
And please read the product description on the product page carefully by clicking on "More..." under "Information".
Quote:
With the Eisbaer, Alphacool is fundamentally revolutionising the AIO cooler market. While classic AIO CPU coolers are disposable products that can neither be expanded nor refilled, the Alphacool Eisbaer has a modular design and can be expanded, converted or refilled at any time. This means that the Eisbaer is not simply an AIO but is based entirely on classic water cooling components. This means it is quieter and more powerful than the average AIO solution.
PS: AIO means All in One.
