To be honest, the questions seem a bit trollish, but I will try to answer anyway.<p>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 &quot;why&quot; and this is the answer.<p>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.<p>Why? Well, these things do not have consciousness and cannot experience pain. There is nobody experiencing &quot;abuse&quot;, not even enough &quot;somebody&quot; 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.<p>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.