MIPS | Pseudo Instructions

Question

Why were pseudo instructions written into MIPS assembly code? Why can't instructions like bge, b, mul, beqz be written in a non-pseudo format?

Answer 1

they can. it is just like directives or macros or other labor saving solutions.

pseudo instructions are not part of the instruction set necessarily they are part of the assembly language which is defined by the assembler, not the hardware nor ip vendor/inventor. Up to the assembler author(s) to define its instruction set.