I 100% agree with everything you said, apart from the last bit, if there is to be a justification for not using a rub, comparing reptiles to mammals wont be it, there are some massive differences in terms of physiology, biology, and anatomy to reptiles and mammals, and their behaviors and habits (energy sources too) and comparing living areas of reptiles to mammals is always murky and moot and it really tells us nothing.
The way I look at it, you can't argue with millions of years of evolution and it is as simple as that, it also comes down to what the keeper will want out of it, for example.
I do co-habs with my snakes (some keepers will frown on this) but my argument is this, I would much prefer to put my snakes together, in a larger more spacious area, with plants, foilage, decor and multiple hiding areas and be able to see them, allowing them excersize, enrichment, the choice to be where they want to be, than I would keeping them in a very small, boring, sterile enviroment, where I can see them exploring, (those who have so far disagreed with my co-habs interestingly have been mostly the ones who keep in rubs) I have yet to hear a well reasoned and constructed argument to the above point though. And again this is my choice, and it is something I get out of it, enjoy and get to see my animals utalising that space, they are oppurtunists, just like every other animal from my observations, and they will take advantage of the things you provide them with (leaf litter) hides, boxes, branches what-ever, but there is differences in how they conserve energy, and put it to use, they are not as active as a dog or cat would be, so comparing the two together and using that anology doesn't really give much, to take that argument to it's extreme if we were to compare them, many cat and dog owners allow them to free roam, if we took that logic then we should all allow our reptiles to free roam