The reason why snakes need some room to move around may be just completely unknown to some people on this thread.
Not all pythons are ambush predators, take the aspidites species, they are active hunters. So are most elapids, not ambush but active hunters.
All snakes need exercise for muscle development and to keep digestion flowing properly. Snakes that don't get exercise, become lethargic and the process of digestion creates gases that need to be released through exercise, otherwise they run the risk of bloating and abdominal pain, movement helps stop this just like in humans!
So as long as there is enough room to move and stimulus to necessitate movement then they are fine. This can be achieved in either an enclosure or a large tub. But those large retics and burmese in the tubs that snakebytes has, well.....