I would imagine one of two reasons. Either they were less expensive to make, or the Fatboy design proved to be more durable. My guess would have to be the former. The Red Dot Fatboy was a combination of the two, but for whatever reason, Gillette only released a handful of them. My best hypothesis is that the Red Dot Fatboy was more durable than the standard Fatboy, but much more expensive to product. Just conjecture, though.