Probably unsurprising but we should be reminded: rent is a HUGE part of the budget for young people, and those who are willing to live in an unglamorous location tend to have much stronger finances than those who live in upscale neighborhoods.

Not just young people. Rent is the single biggest expense in my life. By far.

I think you're right that more of us are choosing our locations more carefully, to save money. 

Why debt to income ratios vary:

• Cost of living plays a huge role in daily expenses. Credit card debt isn't all shopping sprees and expensive dining, and most people put the basic expenses of daily life (like food, clothes and gas) on their credit cards. Living in an expensive city with a comparatively low salary could result in a high ratio.
• Pricey real estate markets also drive up ratios for many of these cities. If you live in an expensive housing market like San Francisco, your salary won't stretch as far as it could in Detroit.
• Good spending habits may factor into your debt-to-income ratio as well, though. Figuring out exactly how much you can spend on luxuries like eating out and entertainment each month is a key part of budgeting, and it starts with taking a realistic look at how much expendable income you really have. If your spending habits outpace your expendable income, you could end up with a high debt-to-income ratio.