Because they aren't as common as BCIs and Dumerils, they're extraordianrly beautiful (IMO so much more so than the previous mentioned species), and yes their size is a benefit. I know many a snake owner who gets to the point where they wish their snake was "just a little bit bigger" after they get full grown.
Feel free to add the previous sentance to the out of context thread.
Don't forget it takes years for a snake to reach "full sized"