My guess would be that someone made an HP out of aluminium, including the grasps because it was easier to machine them than to injection mold a separate plastic part, and then everyone just thought they were too dang pretty to die. Er, paint. I've got an alu HP on my Scrubber-Zilla and it definitely hurt a little to pour "grime" all over it.
Yeah, you're probably right. I mean, I get it - the machined nozzles do look super spiffy in shiny metal. And when the Astromech stuff got started, consumer resin 3D printers weren't available. It takes an extra-dedicated person like zorg to go all out!
Nowadays, however, we can print exact replicas of the Viscount reading lamps using the laser-scanned data from Robert Jackson, so if you do want screen accuracy it's pretty easy.