The companies are incorporated in some country however. And ships that go out to sea must be flagged under some country, and those ships have to follow the rules/regulations of the country they're under.

And their failures cause those same countries non-trivial amounts of money.

Consider the Coast Guard and Navy efforts for this latest event.

According to the news I read, Titan did not need to be classed/certified because it didn't launch from any port. Even if the mother ship did. I'll try to find the citation.