If we learn how "matter has mass" is that going to solve world hunger? Make world peace? Cure cancer?
I just really don't understand or care why matter has mass.
Solving world hunger and making world peace are social, economic and political problems. We could solve them tomorrow, if everyone agreed to the sacrifices that would have to be made, but they don't.
Learning how matter has mass is important for the same reason that any basic scientific research into how the universe works is important. All that knowledge adds up, and allows us to make advances as a species.
Everything we have ever built is based on knowledge of how things work. Say you wanted to build a better garden wheelbarrow. You could look for materials that are light but resistant to a range of weather conditions, are strong, are easily manufactured and are harmless to the environment. And you'd be able to do this because we know about chemicals and manufacturing processes, and how they can be used, because people have studied them in detail, and they've tried combinations of chemicals, and they've drawn on the studies of people in all sorts of fields of research who have looked at things at their most basic level. And this approach applies whether we want to build a fleet of spaceships to carry everyone to a new world because the supervolcano under Yellowstone is about to blow and wipe out life on Earth, or we're designing a new type of needle that can deliver vaccines painlessly, or we're designing a new type of storage medium to improve on Blu-ray, or we're curing cancer.
Knowledge for its own sake doesn't have to mean anything to you, but it's easy to appreciate that you never know when some piece of knowledge will be needed.
