That's how they started out, but there is always pressure to add new instructions for niche markets. But since there isn't any coherent way to implement extensions it means they have to pollute the entire ISA. RISC-V was carefully designed to allow for extensions.
No it was never a [real] RISC. Even the very first version included predication and shift in most instructions. They weren't even fast. The event that changed everything was when DEC Alpha engineers (for reasons I don't know) decided to use their expertise to created StrongARM. This ironically ended up at Intel and was renamed XScale, before being spun out. (EDIT: grammar & typos)
