Adapted from Angelo Mingarelli:
You've discovered, some would say uncovered, something new and pretty and interesting about the mathematical world you interact with, something which may or may not have any relevance whatsoever with the real world but, we believe, that someday all this new abstract mathematical stuff will, indeed, be useful to someone, somewhere, sometime in our future... In fact, many areas that were considered pure mathematics now find themselves at the forefront of application
How could Giovanni Ricci-Curbastro and Tullio Levi-Civita have known, in 1900, that their basic theory of tensors, a very abstract theory for their time, would become the cornerstone of 20th century physics
That abstract logicians would undercover what would be essential to modern day computing
That algebraic topology would be used to study distribution of sensors
That hyperbolic geometry could be used to study the extent and reach of the internet
That number theory would be so essential in fields like architecture and cryptography
That category theory would be useful in studying social behavior.
The list goes on and on.