I bet if you ask 100 people why they bought and if they use bitcoin for anything in particular, 99 will say no. That's why none of this is a real surprise.
On the other hand, apart from appreciation of gold as jewellery (partially because it's expensive) and some industrial use (fraction of the gold industry), in large part gold too exhibits price growth sustained by nothing but a simple cultural notion that it's scarce and valuable. Countries, banks, pension funds etc aren't putting hundreds of billions of dollars worth into stacks of gold bars locked in vaults because of their industrial or jewellery usage, after all. Bitcoin, as little the growth of real-life usecases has been in 2017, may have established itself as an alternative store of value. I don't agree with that myself (just as like I think it's utterly useless to invest in gold as a store of value), but who cares about me.
So it remains to be seen what'll happen the next ten years, maybe it'll still remain as a store of value. I'm no longer buying though. The 'using bitcoin' vs 'bitcoin as store of value' became completely lopsided in favour of the latter, which was the point I cashed out.