The answer to all of your questions: computer programs are written for computers to understand, and computers aren't very smart. Mathematical papers are written for mathematicians to understand, and they tend to be a lot smarter than computers.
Machine language is also written for computers to understand, but it's not easy to read. Computer-formalized math is usually even harder to read than regular notation. I don't think computers have much to do with this.
True, I should have said it better as, programming languages are written for compilers to read, and they're not very smart. Machine language is written for computers themselves. Computer-formalized math I don't think is written for anyone to read.
