They should have one, but they don't, so it allows parasitic companies to trade on the goodwill that the OSI built up. If you don't think that people who sell carbon-based foods should always be able to sell them as organic, or that any coffee buyer who thinks that they do business fairly should be able to label their product as Fair Trade, you shouldn't think companies that are open about their source code should be able to label themselves Open Source.
I'm going to label my company Open Source because we're open about how we source the laptops we programmed the software on. They're MacBook Pros, and you're welcome.