Another major reason breeding reptiles is extremely different then breeding cats and dogs is that reptiles which are not domesticated used to be taken in huge numbers from the wild ( for some species such as ball pythons it was upwards of 20-40 thousand a year) and were desimating wild populations. Since hobbiests could see this number would not curve any time soon as exotic pets were increasing rapidly in popularity captive breeding became the only realistic way to manage wild populations and ensure their was still a way to supply the world wide demand for these creatures.
Back to the orignal topic, while I agree that snakes and reptiles will never show the same affection as dogs or cats simply because they are extremely different in terms of social structure and mentality, lizards do seem to have a igher intellegance level and can develop a very primative bond based on food alone and I know everytime I enter my room, my bearded dragon goliath runs up to the front of the cage to get my attention to feed him. As for why keep snakes. I think it's more just a personal preference, while some morons will get into reptiles for the wrong reasons ( just like some morons who get "tough looking dogs" to impress friends) their are still alot of responsible hobbiest of all ages and background who simply keep these animals out of a pure fascination and love and enjoy the educational aspects of raising them.
I know personally I love having them around and always try my best to reproduce their exact wild conditions and give them a stimulating and large enviroment, though arguing the ethics of keeping animals in general in captivity especially exotics is going to vary widely from person to person, I can simply say that if you do choose to own one of these fascinating animals you owe it to them to care and provide them with only the best as they will be completely dependant on you for the rest of their lives.
I find having them around very relaxing and love to handle and interact with them, it's hard to explain but I have a deep rooted love of them and always have.
Just my thoughts though
Here's myself with Kaipo my big puppy dog
Lastly just wanted to note, that being unpredictable is not limited to pythons or boas alone, and that any and all wild animals are ultimately just that; wild. You can learn to read their body langauge but if you are working with a species large enough to cause you bodily harm or death its your responsibilty to ensure you take nesicary precautions. Know your reptiles individual personality and temperment and act accordingly around it.
Cheers
Kayla