Actually, it’s a matter of both. There is a thin line between these two. When you want something, you feel you need it. You might consciously or unconsciously trick yourself into buying something you don’t absolutely need but you want. As simple as that. But let’s not play with words here.
However, what I meant to say to the OP is that we need to accept it as a fact that the speed of today’s technological advancement is forcing us to stay up-to-date. I have nothing against your logic or the post by HughH.
Let me give you an example: I was quite happy with OS X 10.6.8. Steinberg doesn’t support that OS any longer, so I was kinda forced to upgrade to a new OS in order to make sure my new Cubendo versions would run hassle-free. And I’m praying to God that I wouldn’t be forced to use Win 8 or buy the new Mac Pro as I’m quite happy with my current system. I do hope I’m making sense this time, since English is not my mother tongue.