It's not just income though- people like to spend at least some time with their partners, and from the article:

"Eric’s duties as partner had slipped drastically behind his personal ambition to perfect the game. He guiltily recognizes Amber felt lonelier and lonelier as he pushed on, but he did little to address it—he still worked 12 hours a day on the game, often going straight from his desk to the theater for an evening shift."

This is an entirely different level than a stay at home spouse. The article mentions he worked part time during this period, and that his girlfriend is currently attending college. So this is not a situation of a sole income earner, but rather a man so obsessively dedicated to a project that it consumed nearly all aspects of his life.

They do if they end up divorced. If you are earning enough money to support your spouse, guess what? If you get divorced, you get to continue doing that!

You will support your spouse directly via alimony, usually for a period half the length of your marriage, but if you were married 10 years or longer, this does not apply and there may be no set end to alimony. Mine was $1800 per month for 4 years.

I have 40% shared custody of my kids (they actually spend more non-school hours with me, but I digress) and still have to pay $1700 per month in child support, because (at least in CA) you are required to maintain the same standard of living as the children had during the marriage.

It may not be about income and finances during the marriage, but if it goes wrong, and you are the one that has been providing the support, prepare to swallow some very bitter pills.