I don't find it depressing, personally. Yes, it's one way a career can go. It's a lot less money than I make at my day job now. But when I do leave my day job, if I were to make $18k a year from writing in addition to being a TA and a military reservist, I'd be OK. I'd make a decent middle class salary altogether without seeing the inside of an office building, and I might be fine with giving up my current shoe-shopping and restaurant-hopping spendy lifestyle for an office-free my-own-schedule lifestyle.
No, it's not the same known salary and stability of a professional day job, but we all know that. The risks have their rewards, even if you never make the NYT best seller's list. Or at least, that's how I feel about it.