I for one am super excited about the potential of RISC-V to liberate our computer hardware :)

There are f.E.:

https://www.openmotors.co/product/tabbyevo/

https://hackaday.com/2022/02/23/novena-open-source-laptop-reborn-as-desktop-machine/

https://www.crowdsupply.com/eoma68/micro-desktop

https://www.kosagi.com/w/index.php?title=Novena_Main_Page

More

https://en.wikipedia.org/wiki/List_of_open-source_hardware_projects

Search open hardware projects, not open source, with the last you searched software, not objects.

I think mainly because it's a lot harder to make a physical object than software, so the smaller players and nonprofits who support open source are essentially unable to compete with conventional hardware companies, who have no desire to go open source.

It happen because unlike software (programs) that is governed by the licenses (copyright) the hardware (physical objects) is governed by the patents, and mostly of the time these patents are share among several manufactures, and sometimes they are extremely ridiculous (you can patent practically any idea, no matter how simple and unclear it may be) that whatever product you bring out you have probably violated some of these.

Because money? Currently it's not a small feat to achieve and people/companies want to be compensated and make profit off of it.

Open source hardware projects rely heavily on grants and donations for which most people are hesitant.

Everyone here is most welcome to my talk on libreplanet which would occur in a couple of days, Survival of Free Software

My guess would be due to competetitve advantage and a lack of economic incentive. It takes a lot to build any number of those things and a lot of them benefit from trade secrets that likely would be public if the whole thing was open source.

That's kind of been happening with 3d printing. I think it's just not profitable to do it as a business there's a ton of competition in manufacturing that IP can be make or break

It's a matter of time. Just like with software, you have to have a bias toward open source, freedom respecting objects and support them with your cash.