"A desire to learn" and "Make new contributions to human knowledge" are laudable goals that I admire. But, even leaving aside the important question of whether grad school as it is currently structured is a good way of pursuing either, it's hard to make new contributions to human knowledge when you're having trouble making enough money to support yourself, and it's frustrating to see your new contribution made when your buddy is working for Google and writing software that millions of people use every day—and getting paid well for it.

It seems not unreasonable to me to balance life / career goals with learning and wealth. The opportunity costs of grad school are incredibly steep. If you are the rare person who doesn't care at all about material possessions or the physical quality of life, then by all means go to grad school. But if you go expecting a tenure-track job at the end—which most people seem to—then you're making a mistake. I am not at all opposed to someone who simply says, "I don't care at all about income."