That's also what I'm wondering. For my primary work PC it's: Either it's really portable and has a screen - then it should be small. Or it's not portable - then I don't care as long as it fits on or under the desk.

For some environments however small or invisible hardware and the associated clean look is definitely a bonus: E.g. if it's a PC in your living room (I bought a NUC for that), or maybe for publicly exposed working places (receptionist, ...). But that's not really what is targeted with that hardware.