In this day and age: when they are 'marketable'. When they are desired by 'someone else'. When they are so astoundingly hilarious and functional apparently!
Thomas Schnur presumably keeping it from climbing the walls. Maybe they live in their own house or a rubber zoo. What games would they play when he is not looking? Would they need sleep?
One thing is for sure: it's a table and it is travelling: Hong Kong and New York to name a few.
Source and photos: http://www.agitatto.com/blog/?p=9937