RISC-V doesn't necessarily need that much software though. You are thinking about RISC-V as the central CPU of a desktop computer. However a lot of specialized accelerators and co-processors are being built using RISC-V.

For all we know Apple may even put RISC-V CPUs on their SoCs to handle things like encryptions, video encoding, machine learning and other specialized tasks. As a software developer you would never see the RISC-V chips. They would be utilized by Apple specific frameworks.

But why use RISC-V for this rather than ARM? Because RISC-V can easily be tailed to different tasks. You only have 47 instruction you must implement to make a RISC-V chip. The rest can be specialized stuff for e.g. what you want to accelerate. An ARM chip has over 1000 instructions. It is a large complex general purpose CPU, not that well suited for specialized tasks.

RISC-V also offers and advantage to low end feature phones. These phones don't need large software stacks. What matters is cost and batter life. This is an area where RISC-V can outcompete ARM due to simpler design.

For RISC-V to threaten ARM on the smart phone market, servers or desktops as the main CPU will likely be many years down the road. But RISC-V may very sneak its way into your hardware as specialized co-processors.