HAHA!
How does this knowledge help to answer anything? It provides information about something "real". What scientists will do with this information is up to them. Think of this world as a big puzzle. Proving that Dark Matter exists, is a puzzle piece that has been added to the big picture. It's just a small fragment, but maybe it helps someone else add another fragment.
Mathematics has a lot of pseudo-futile theorems, proofs etc., but even if they're futile right now, they might become useful in the future. When group theory was developed, nobody saw its potential in physics, chemistry, cryptography... yet today, they use group theory in all those subjects.
It's better to have some information that is "true" and maybe never use it, than to not have it.