Can it not be both? Someone can want to learn for the sake of learning, and then filter further using practicalities. I'd love to learn every programming language out there, but it wouldn't be possible, we only have a limited amount of time in this life, so I'll instead learn the ones that are the most practical to learn. Java, however practical, may not be interesting to me so I may not learn it. Piet is super interesting, but not all that practical so I'll probably never learn it.

It doesn't have to be a single variable equation. I can learn something both to learn it and for practical reasons.