If you've kept any other snakes besides BP's, you will understand just how much BP's hide, and how difficult their temp, humidity, and secureness requirements are.

We have a beautiful orange corn snake that never uses his hide, he's active during the day, and we have him in a nice natural set up that's easy to fill his needs. He doesnt need high humidity, or high temps. He has a tree he likes to chill in, and he also likes to burrow through his substrate. He get's a lot of stimulation from being in a nice natural set up, and he's out for us to view him all the time. He's a great display snake and easy to take care of in a tank, whereas the BP's aren't.

Plus, like someone said earlier, it takes a lot of effort to keep those large cages clean.
Your BP will thrive in a nice tight space where the requirements are met. This is easily met in a tub, but can be made in a nice enclosure.

When designing an enclosure for a snake, you have to put their needs first, and our desires last. A tub is a great way to fullfill all of their needs simply, but tanks are a harder to get the hang of to fullfill those same needs. That's my theory behind tubs.