Because stuff costs money? Financial stress is the leading cause of friction in relationships: http://www.cnbc.com/2015/02/04/money-is-the-leading-cause-of.... Something as small as getting a parking ticket ($50 here in DC) can cause a lot of stress for a family for whom that's not something they can just wave off. Also, high status jobs are usually a lot more interesting. A lot of people would code for free--nobody would restock shelves for free.

And women strive for status and money too. Women outnumber men in college--and it's not because they're trying to improve their prospects on the marriage market.