The thing is that to translate code to binary you need to know binary and write your compiler accordingly and Assembly being the first programming language to exist is the closest thing to binary that is kind of readable-ish (with great emphasis on kind off) but translates directly to binary, every line of code in assembly is binary instructions just polished to "look" human readable, so you'll find it used in compilers for high-level languages, the language used to create operating systems, and non-wasting memory perfect applications