if you aren't running on the gpu you're leaving 80+% of your computer's performance on the table. no optimizing compiler is going to make your legacy c or lisp or rust code run efficiently on the gpu, or even in most cases on a multicore cpu. nor, as thechao points out, can it compete with assembly-language programmers for simd vectorization on the cpu

in summary, optimizing compilers for c or pascal or zig or rust or whatever can only be used for code where considerations like compatibility, ease of programming, security, and predictability are more important than performance

probably the vast majority of production code is already in python and javascript, which don't even have reasonable compilers at all