It will be used when it needs to be handled. e.g. where elsewhere, an exception would actually handle it. Which is seldom the case.

More instructions doesn't mean slower, either. Superscalar machines have a hard time keeping themselves busy, and this is an easily parallelizable task.

>The designers of RISC-V included the bare minimum needed to compile C, everything else was deemed irrelevant.

Refer to "Computer Architecture: A Quantitative Approach" by by John L. Hennessy and David A. Patterson, for the actual methodology followed.