It's... not? Like, if you want to merely use an ISA, you don't need it to be simple or easy to understand, in fact tons of people pride themselves on making extremely high-performance RISC-V cores with OoOE and so on.

But the reason why someone might want a C implementation of an ISA is different from the reason people might want to go implement an ISA in a real project: maybe they want a software simulator that is easy to understand for one reason or another, perhaps for learning or demonstration purposes, or just as a fun hobby project.

These people wouldn't benefit from just pulling down Verilator or using one of the existing BATTLE-TESTED INDUSTRY-STANDARD PROFESSIONALLY-AUDITED HIGH-PERFORMANCE implementations because they literally don't care about any of those things.

In any case, it's a fallacy to assume that every programming project out there has to address a need in order to have a place. https://justforfunnoreally.dev