Linux

The same thing happens with Intel and AMD. A Linux distribution has to pick a hardware profile when they build all their code.

On x86-64, you are running code which is not completely optimized if you are running super modern hardware. That said, the performance penalty is not very big and the benefit is that the binaries are compatible with processors released years ago.

For RISC-V though, the capability difference between the stuff in the market today and the next gen is going to be significant. As a distro, you have to decide what hardware to build for. If you choose older processors, you will be leaving a lot of the next-gen capability on the table when using newer chips. If you require the new architecture, existing hardware will not make the cut.

It is just an ecosystem maturity thing. The RISC-V standard that Ubuntu is demanding reaches feature parity with AMD chips from 10 years ago (about the generation that most x86-64 distros target). So even as RISC-V advances, this new profile will probably remain a decent build target for Ubuntu. I can see why they would want to make it the standard for their distro at this point.

There are server chips appearing with these RISC-V features. This will position Ubuntu as a go-to distro for those systems. And Ubuntu will be ready in the SBC and desktop space when capable chips begin to appear there.