You can think of LIGO as being the first new way to directly see the universe since the invention of radar telescopes. Our ability to measure the otherwise unmeasurable, such as black hole and neutron star collisions, could lead to a better understanding of dark matter/dark energy, astronomy, and both physics and astrophysics.

This expands the reach of knowledge of humanity; once made available, who knows how future humans will use these new discoveries to benefit mankind. Claude Shannon developed information theory well before networked computers were invented, but it's now critical to many disciplines and products you use every day.

Meanwhile, the actual engineering challenges overcome in the building (and refinement) of LIGO are directly applicable to development of more accurate sensors, quantum computing, and precision engineering - all of which will touch the lives of Earth's inhabitants without most of them even being aware of it.

Like a number of other large scale scientific instruments like the LHC, it's provided proof of theories held for a long time - in this case, that gravity can propagate in waves, and that merging black holes cause these waves, and in turn that black holes do in fact merge or rotate around each other causing huge waves in spacetime.

Is it conclusive evidence? No, ultimately it's just a data point. But it's evidence.

Take another one; Einstein hypothesized that light is influenced by gravity, and came up with an experiment that didn't need super high tech instruments; observe the stars next to a solar eclipse and see if their position is different from normal. A few years later there was an eclipse, multiple people made the observations, and his hypothesis was proven correct.

Thanks to that experiment, we now have telescopes that can use gravitational lensing from galaxies to look at the farthest reaches of space.

What possible purpose could learning more about a hunk of random crystal and some electrodes have? Oh, that seems to have some interesting properties after all.

Some crazy dudes want to build a flying machine. Totally impossible, it will never happen. Just stick to horse-drawn carriages, also let’s try to squeeze a bit more efficiency from that coal-powered steam boiler over there...

And on and on and so forth. Breakthroughs and just general advances in science look like crackpot ideas or wastes of time until they aren’t. Fundamental research is almost always a good thing, no matter how out there or wildly impractical it may seem.

LIGO by itself serves "very little" purpose, just watching for gravitational events that are theoretically possible and checking if they happen for real. It actually confirmed that these events exist a while ago[1], and now it's "just" looking for more things we already know exist.

in my opinion, the point of LIGO is no longer in detecting these gravitational events anymore tbh. Doing that is cool, and will bring us more data points about the events, but it's unlikely to ever yield "new science" like that.

Instead, LIGO (and Virgo) excel in exactly the kind of thing that we see in this article: to push the barrier of what we can do in this hyperspecific use-case, finding ways to do "new" engineering that would not make sense for other commercial projects yet and finding out how to implement cool solutions. The fairly consequent amount of funding and the extra focused goal it is aiming for will lead to new techniques and technologies that might have an impact.

Now, is there a guarantee that this new technology will have a larger impact than "better detectors"? No. Actually, there's no guarantee about anything coming out of LIGO ever, no more than out of the LHC[2] or ITER[3] or the ELT[4] will give us new science. But putting all of your eggs in the same basket is a bad solution for making more science, and there's enough room in science budgets to try a few dozen monumental projects and see what sticks.

[1] https://en.wikipedia.org/wiki/First_observation_of_gravitati...

[2] https://en.wikipedia.org/wiki/Large_Hadron_Collider

[3] https://en.wikipedia.org/wiki/ITER

[4] https://en.wikipedia.org/wiki/Extremely_Large_Telescope

What's the purpose of a baby? Is it just a future worker, or does the baby have intrinsic value?

What purpose did the moon landing have? It didn't benefit anyone!

But the surrounding research and advancements in all scientific fields did!

The point of science is to learn. Maybe there's nothing practical to LIGO, maybe in 200 years we have artificial gravity. There's no way to know.