Seems like having a big and clunky external power supply enables a smaller profile for the rest of the unit while making installation a bit more complex. How exactly is this thing going to be installed for use? Wouldn't it be easier to just have a bigger box with more shielding and heat dissipation?
External power supplies make UL certification cheaper; that's the reason. I hate power bricks but I have so many on my desk that one more makes no difference. The Beelink version has an internal PSU BTW.