Because we can!!! :-D
It adds to the versatility of the computers. like you said the Efika is not intended to be a desktop computer. and apart from embedded operating systems there is AFAIK only two OSes available to Efika, Linux and MorphOS.
Aros would be a great addition.
a lot of Amiga users have Efika now. and more will come. and it is nice to have the the freedom to choose an OS that you are comfortable with.