I understand what you're saying here, but I'd have to disagree, even though it makes perfect sense. Reptiles and other herps are simpler in comparison to mammals. Mammals can observe and learn from their surroundings, and can also pick up habits. Herps, on the other hand, are much older and more simpler creatures. Because of this, they act purely on instinct rather than impulse. You can teach a dog to sit by saying 'sit,' and giving him a reward whenever he gets it right. But a snake, on the other hand, won't ever be able to obey a command, no matter how many pinkies you give him. Their brain just doesn't work that way.
As far as herps growing more and more confident with being handled over a few decades or even centuries, I highly doubt it will ever be possible, simply because they cannot learn.