There are tricks we use to convince ourselves to buy the newest, most powerful devices. I myself have an entire quiver full of these tricks.
I've read a number of posts recently in which someone claims that buying the biggest, fastest iPad, iPhone, MacBook, etc. will "future proof" their purchase. I wish I'd have written them all down, but here's one recent example from Federico Viticci at MacStories:
The way I see it, this year's 1 TB iPad Pro is the iMac Pro of iPads – the very best that is going to serve me well for years to come.
That sounds like a good plan, and one I often use. But, and I could be wrong, I have serious doubts that he'll still be using that particular iPad for "years to come".
We should just admit that we like having the best option currently available, and will buy the latest, greatest model every year or so whether we need one or not.