I don't know about everyone here, but I have never upgraded my enclosures. I am no expert, but I have successfully raised 2 bps without ever getting them a bigger enclosure. The 2 youngsters I have acquired in the past were both under 300grams, and were put straight into a 48''x18''x18'' tank...however there were numerous hides (2 identical ones, one on each side of the tank) as well as numerous fake plants and foliage for hiding places. They eat, poop, and sleep just like any normal snake does.
I think giving anything the "bare minimum" is a little silly. I also have a crestie, and the moment I brought her home she was in her 18x18x24 tank and never had an issue with her either.
Think about it for a second...these animals come from the wild...where yes the bps spend most of their time in termite mounds and such, but they do come out and look for prey...and not just in a 3 feet area.
Just some food for thought.