The verification itself is valuable because it gives us confidence that the software is correct. This knowledge changes what we do with the software. E.g. do we need to sandbox it before processing untrusted inputs? Is it safe to put it on a hostile network? Can we use it to control an airplane or a nuclear reactor? Even if the code remains identical, formally verifying software improves it because it lets us use it in situations where unverified software would be too risky.