There are many definations of "hacking." If you consider hacking to be using one computer to gain access to another computer, then social engineering isn't hacking. That is not what most people consider hacking. To most people, it is unauthorized access to a computer system. In that case, social engineering is a means to an end. And it doesn't always include lying. I have gotten necessary network infromation from teachers that gave me access to certain computers on campus without ever lying to the teacher.

You could also go to a broader sence of the terms. Hacking "used" to be doing something in a way that was not normally done or had never been done before. If your muffler comes off your car, and you put it back with a coat hanger, you have "hacked" it together. The ARPA net was originally a big hack job. So was ENIAC. The point is, there are many forms of hacking. Therefor, there are many forms of Social Engineering. It is simply a term used for getting information from a person that you wouldn't normally be given. It doesn't necessarily mean that you lie to get it, although that is a possibility, it just means that you get it. And you get it from a person, not a computer.