any hacker can, in the next ten minutes, cause their CPU to do more arithmetic than the arithmetic (explicitly adding 2+5, and so forth, multiplying two numbers in their heads) that every single person has done in the history of humanity. okay, but that's just numbers.
Today we live in a connected world where 2,000,000,000 people can be reached in any eight-hour period of time.
Any hacker can find any niche and make a product that will be the first search result within it (by being the first; making something that doesn't exist; and telling people).
Why save a salary, when you can create a business, create value, and scale to the entire Internet and give people some benefit?
Every hacker should start one or several businesses. While it may not exactly be a moral obligation, this brings humanity forward.
EDIT to clarify: I am disagreeing with the suggestion that hackers should save all or most of their money - (put in my parent comment as "save as much of your salary as you can") -- rather than saving it, they should invest it into their businesses, adwords to grow it, other advertising and business development expenses, hiring, etc.