Comment by dgroshev

To add to this, constructive solid geometry systems like OpenSCAD seem to be practically incapable of doing anything related to surfacing, even if it's just G2 fillets or G2 continuity (much less more advanced work with splines and patches).

I think it's partially a positive feedback loop: the "hacker" tools (OpenSCAD) influence the aesthetic (blocky/square brackets, like in the post), which in turn influences the tools. When creating a simple fillet or a chamfer is an annoying exercise in constructive geometry rather than five mouse clicks, there'll be fewer fillets, chamfers, and flowing surfaces, even when they make mechanical or manufacturing sense; but then that becomes "the look", and people don't even think about fillets.