Are Academics Irrational?

My main nerdiness is philosophy. "Why study that?" is a popular question. Typically, my answer is, "I'm wired weirdly; I just like it." I rarely defend it further.

Like a good self-doubting philosopher, I wonder whether I could defend it further. Yes, I can offer reasons to think that philosophy is important and valuable. But that might just be rationalizing NASA with Tang: while there are benefits to the space program, it's not clear that they warrant the resources devoted to it. Likewise, perhaps the effort I spend on philosophy just isn't worth it.

The opening quote of the documentary The Linguists got me thinking about this: "Around the age of eight or nine, I discovered I had a somewhat irrational interest in the world's languages." At first pass, this sounds right. Devoting one's life to the study of dying languages isn't obviously more important than devoting it to the study of, say, penguin digestion, or the antebellum South. Why choose linguistics, then?

It seems, then, as if academics face the same charge of wasting their lives as nerds do. Is academic specialization nothing more than the illogical passions of a group of nerds?