Why can't programs be proven?

Question

Why can\'t a computer program be proven just as a mathematical statement can? A mathematical proof is built up on other proofs, which are built up from yet more proofs and

Answer 1

Most answers focused on the practice and that's ok: in practice you don't care about formal proofing. But what's in theory?

Programs can be proven just as a mathematical statement can. But not in the sense you meant! In any sufficient powerful framework, there are mathematical statements (and programs) which cannot be proven! See here