Why not? Why, indeed, would wizards with enough status and wealth to turn their hands to almost any endeavor, choose to spend their lives fighting over lucrative monopolies on ink importation? The Headmaster of Hogwarts would hardly see the question; of course most people should not be powerful wizards, just as most people should not be heroes. The Defense Professor could explain at great and cynical length why their ambitions are so trivial; to him, too, there is no puzzle. Only Harry Potter, for all the books he has read, is unable to understand; to the Boy-Who-Lived the life choices of the Lords and Ladies seem incomprehensible - not what a good person would do, nor yet an evil person either. Now which of the three is most wise?

I can't say that Quirrel is more wrong than Harry, but Dumbledore's position ("of course some people should not be powerful wizards") is fatuous in his own universe, much less in the real world. It might turn out to be right, but there's no of course about it. In short, my only assertion is that Dumbledore is not qualified to be our moral ideal in an imperfect universe, even if he is a better choice that Fawkes.