No history actually tells you that only 1% of produced maths is useful. You only see the good stuff not the ugly stuff.
The core of the original comment that started this chain was:
> Applications of pure math happen downstream decades or centuries later.
My argument was that history shows that a surprising amount of mathematics does eventually trickle down into applications. I don't think anyone is arguing all of mathematics eventually sees an application.
Again, my point was that history does indeed seem to show that "applications of pure math happen downstream decades or centuries later". As the original commenter said, it's hard to predict what will be the next thing to be applied.