The guy selling food on the street has liability in proportion to his profits; fifteen customers, fifteen potential food-poisoning cases. He can set his prices accordingly. Simon Tatham doesn't have any profits, but his PuTTY is installed on every developer's Windows machine. OpenSSL is installed on even more machines. How long do you think it would take your proposed regulatory regime to find that Kurt Roeckx owed several million dollars to every company that generated private keys with Debian's copy of OpenSSL? He did, after all, introduce the subtle security hole that left them wide open for years.
Maybe you could make the case that he was following best industry practices in doing so; after all, using Valgrind is a best practice, right? But you could also pretty plausibly convince a jury that he was negligent. Especially if you're IBM's senior counsel. Or, say, RSA's.
Now, is Kurt Roeckx or RSA going to be advising the US legislators who draft this candidate legislation, establishing the standards that they both must uphold?