No I don't have a complete understanding of the law in this area, but in simple terms it is because Google's search engine is designed to give users the most relevant results, and by giving their own brands preferential ranking (without an advertisement notification) they are misleading users and giving their brands an unfair advantage over their competitors.

I'm sure someone else here can go into a more detailed answer.

Side note: the only "meme" I've noticed is the idea that anyone would be presumed a lawyer unless they say "IANAL".