Single board computers are numerous, mostly but not entirely at the low end, and no cabled interconnects is the defining trait of the class.

The reason we don't see as much of this in full-size desktops is because density is clearly not the objective and it would mean sacrificing the modularity and flexibility of established standards.

Or in other words, more expensive with no real gain besides aesthetics, which aren't worthless but I'd bet they aren't worth _much_ for a box which spends most of its time under a desk concealing its insides.