Most mortgages require that an appraisal or at least inspection is done before any loan is made.
There are exceptions to this, in the form of no-appraisal mortgages which are available to lower-income homeowners, qualifying members of the military and its veterans, and some farmers. Most no-appraisal loans are through federal programs such as HARP, FHA, and the VA.
The purpose of these loans is to keep people in their homes and to keep the economy relatively stable. These are generally not first mortgages, but are relief, modification, and refinancing arrangements to qualifying homeowners that already have a mortgage outstanding.
Many large investment and banking institutions have a significant stake in the mortgage market, often in the form of collateralized mortgage obligations (CMOs), even since the housing bubble and crash of 2008, but there are still a lot of precarious loans out there.
Through the HARP program and other legislation since 2008, the federal and state governments have been trying harder to offer relief to consumers who may not otherwise be able to continue making their payments. It could also just be an added benefit available to those who served their country with military service.
When was the Latest Housing Bubble?
What is a No-Cost Mortgage?