Like I've said many times: LLMs are useful for this (i.e. porting software from one programming language to another).

Porting software is painstaking grunt work which still takes a moderate amount of intelligence. It's therefore extremely expensive to port say, COBOL banking software running on mainframes, to another language like Java. That's why a lot of COBOL software is still in use. I expect this to die out in the coming years as many of these systems will finally be ported to another language (could be Rust or any other language).