The debt-to-income ratio includes monthly payments such as your mortgage, car payments, student loan repayments, and child support.
However, it doesn't include payments such as auto insurance. I understand auto insurance isn't exactly defined as a "debt" (although home owners insurance is included within DTI). But this is in essence, nondiscretionary income... why don't lenders look at this?
Is it because it varies too much? Or is it because it doesn't affect the riskiness of the borrower (at the end of the day, these loans become assets to the lender, whether they retain/sell servicing or retain/sell the loans in the secondary market).