[Pamar]

To be honest, the questions seem a bit trollish, but I will try to answer anyway.

a) Homo sapiens is a social animal (you can check this on Wikipedia if you are unfamiliar with the term). Therefore it tends to confer special status to members of its own species. I am not saying this is right or wrong - you asked "why" and this is the answer.

b) In part this has the same answer as (a): we (humans) tend to privilege other humans (or species we find socially valuable, like dogs and cats) and have much less problems in using other animals as a fungible resource. But even an ethical vegetarian or an animal rights activist would not say that cars, toasters or macbooks should not be traded, used, and finally scrapped.

Why? Well, these things do not have consciousness and cannot experience pain. There is nobody experiencing "abuse", not even enough "somebody" to experience pain or discomfort. If you are ok with the idea of selling stones or kicking sand around, you should be ok with scrapping laptops, too.

When (if) machines reach the point where they actually experience things, then we will have to deal with that. Hopefully ethically. I doubt it will happen soon, though.