Why is it so difficult to get a tiny mortgage?

Obtaining a mortgage of less than US$50,000 for a tiny home or even a refinanced "traditional" home is a challenge. This interesting Business Insider article indicates that banks simply don't make enough profit compared to the the interest they reap over a couple of decades on mortgages of a couple hundred thousand dollars. Fortunately, there are alternatives such as local banks or credit unions where you have an established relationship, personal loans from friends or family, or the relatively new phenomenon of peer-to-peer (person-to-person) lending on sites such as Prosper.com and LendingClub.com.