That's the motto of Carleton University, where I work. Carleton's task, and my task, and the students' task, is to produce educated students. It takes a lot of resources to do this: my time, the students' time, the support staff's time, plus the use of buildings and land, and hydro. All those resources could be doing other useful things. There's an opportunity cost to educating students. Why do we do this?
Because we think the world will be a better place in future if we do this. And it's not just that the more productive students will get higher-paying jobs and more enjoyable jobs, though that's part of it. We think that it's better to understand things better, whether that thing is economics, chemistry, or literature. My blogging is itself part of that task, and if you are reading this you are a Carleton student, and part of our common task, whether you have a student number or not.
What do economists call it, when you do something that is costly today, because you think it will produce future benefits? We call it "investment". Investment is the creation of capital. Our task is to create capital. And that capital, in our case, is embodied in humans. Which is why it makes sense to call it "human capital".