It's a proper pure math problem - it doesn't have to have a use, it doesn't have to have an application. Like Fermat's Last Theorem (FLT), in and of itself it's probably of no value.
However, there will be an answer. It might be that every number returns to 1, it might be that there is a loop, it might be that some sequence goes off without bound, and it might be that the answer is unprovable within the usual axioms of mathematics.
But currently we don't know. And as with FLT, it might be that while the problem itself is of no use, the techniques developed in the attempts to solve it might prove to be amazingly useful.
Currently, no one knows.
There are lots of people who just don't care about something unless it has immediate and obvious uses, and that's fair enough. There are others for whom the interest and excitement is in the chase, and that makes it worthwhile.
Several prominent mathematicians have said something along the lines of "we would need a much different math to solve this".
And this is despite it being simpler than every problem being actively worked on in mathematics (e.g. Riemann hypothesis).