[TheRealPomax]

Until it's not, because someone suddenly realizes that a seemingly completely unrelated problem in a completely different subfield that's holding up a major proof is actually analogous to a problem where this result removes a bunch of roadblocks.

That's the problem with math from a "so what is this good for?" perspective: we don't know yet, but we sure have a litany of instances where seemingly useless proofs had a profound impact anywhere from weeks to centuries later.