I believe it was the concern of looking like a pyramid was the reason to not.
Two levels does not make a pyramid; I'm pretty sure you need at least one more.
By the way, pyramids have a bum rap. They appear on the US dollar bill. Strongest structure known to man. The ones in Egypt have lasted for more than 4,000 years and it's not an accident that the best preserved ancient structures in other parts of the world also have a similar form. Every organization in the world, public or private sector, essentially has a pyramid structure. And there is no better marketing structure in the world than some form of pyramid; as long as you are not requiring people to pay in and you are not paying out more than is sustainable, then it's not a ponzi. Nearly every Fortune 1000 company has a similar marketing structure. Etc. etc. Though I do understand that perceptions are important.