Selfish people

What is it with selfish people who don't ask about others things and use them without thier consent? , even if they use or give away other's belonging infront of them with out asking the person whose thing is being given away if it's okay , and that person can't say "This thing is for me" , because the one taking it is in an angry mood , and the thing is if it haapens to be that a person took a belonging that's for them and used it or gave it away ,then that person will get very mad .I mean , who gave them the privilage to use others things or give away others things while it's not okay for others to do the same to them ? .