You make an excellent point, although the design of almost every other component has gone for sleeker and more gilded styles making motherboards look sort of "naked" in contrast. For instance my build has a 3080 FE and a Black Noctua NH-D15 (with the covers) but my raw motherboard really detracts from the look. Both are beautifully designed components with none of the Gundam armor nonsense so many components are covered in. While the design fetishist in me loves these NZXT boards, sadly the specs and performance never seem to warrant a purchase.
That said I'd love to see an all "nude" build. Where ALL components are as raw as possible flexing all their glorious complexity. Something like the old school controllers hotaru251mentions. Build it in a clear case so it's like the desktop equivalent of one of those controllers. That would be something.
It's because that's a very dated 80/90s look, and despite your personal affinity for it, is an eyesore for the majority. Most motherboards can be stripped of the covers, armor, etc. and you can remove or modify for the same with your PSU, GPU to produce the look. I used to run clear plexi top covers with an anodized lower for my PSU back when almost everything was a raw metal-colored box. Instead of complaining about the manufacturer not making the part exactly how you want it, modify your build to suit your personal preferences.