Uh they do 'require' much more space. You do know that a 4x2x2 is roughly 120 gallons, right? A ball needs nothing more than a 40 G breeder (max right?)....so more than double would be "much more" in my eyes.

They are semi-arboreal, I wasted about $30 on branches and stuff that mine never used when I use to use a light. My RTB stays in the hide more than my ball.