If you're "using RISC", that means that you're producing something that involves a processor. If you're just making software you just need to have it compile with common compilers and have the relevant libraries available on your target platform (ok, I'm over-simplifying), so you don't "use processoer X over Y".

When you do use hardware, you're interested in things like power budget and price for comparable performance. RISC-V is now reaching competitiveness in some cases, and companies/people will now start choosing to use it on the merits. If, there is, there's an OS available and a bunch of supporting tools and libraries.