I appreciate the coolness factor. But, unless the payload can be enough to pull off a 1998 Bruce Willis, what's the immediate benefit? Or, would this be fundamental to some research?
Regarding Omouamoua, we just observed for the first time in human history, a cylinder or plate shaped object from another star flying through our solar system with questionable orbital velocities (we are not quite sure how to explain a small acceleration it had). A cylinder/plate is not a low energy geometry (things like to turn into spherical type objects over time), it's from another solar system, we don't know very much about it. How could you not want to visit it?
It's an opportunity to pull off a speed and distance record, visit something from another solar system, resolve big research questions about its shape, composition, origin and rule out any theories of its possible intelligent origin. They are also pursuing it to showcase the benefits of nuclear heat for space.
This is a more of an etymology issue than what you think, if you need to look up the word etymology, I'm referring to the the history of the words and not suggesting any changing meaning
Search for evidence of life outside the solar system. Unless you're planning a trip to another star system this is all we've got in our lifetimes.
Hitching a fast ride to the outer edges of the solar system since it's on a hyperbolic trajectory.
What is the asteroid made of? That shape of asteroid is not normal. Usually they're rubble piles, these were different. Is there formation methods we don't yet know? Were they fragments of a planet's destruction?
On an engineering level, we've never had to rendezvous with something on this trajectory before. Can we?
That is how progress works. Lots of things were researched or invented before progress in other areas (materials, economics, society, other scientific finds...) made these findings useful or even feasible. You never know when and why you will need this, the only thing you know - it will be used eventually. Maybe this will give some important clues into the future interstellar travel, maybe the tricks and technologies invented for this mission will be used elsewhere, maybe sample will give important clues into the origins and probability of life.
People often claim commerce and free markets are the driver of innovation. That's true, but they're not the only driver. Industry and national "moonshots" play off each other very well.
It's an opportunity to pull off a speed and distance record, visit something from another solar system, resolve big research questions about its shape, composition, origin and rule out any theories of its possible intelligent origin. They are also pursuing it to showcase the benefits of nuclear heat for space.