My ball pythons do not climb. However, my corn snake is a different story--she burrows into her bedding AND somehow, though she is only 4 months old and teeny tiny, has made it to the top of the 10 gallon tank she resides in, where she hung for several hours (wedged between the lid and the tank itself). I have NO idea how she got there.
As for BP's climbing, you could say it either way, but perhaps it's that "they only use what is there". If they have a log to climb, perhaps some will seem happy to climb and explore, but if they don't have one, they will never miss it or suffer. Ball pythons in the wild prefer to live in grasslands, savannahs, and SPARSELY wooded areas. Most of those places have tall grass but not much for trees.
I definitely think they're happy in a tub, but they're probably just as happy in a tank (with proper temps and humidity), with or without something to climb.
If you didn't know soda existed, you wouldn't want it....right?