Since 1999, the residential mortgage industry has been greatly affected by two events. The first of these was the repeal of the Glass-Steagall Act. This act was passed in 1933 and separated the commercial banking and investment sides of banks.
The second event was the Great Recession, which started in 2007. This second event forced banks to change their practices, often whether they liked it or not.
One of the results of these two events is that traditional banks don't have as many mortgages as they once died. Traditional banks used to have a 90% share of the residential mortgage market. Since 2009 that has declined to around 50%. Lending standards are much stricter and so people that don't qualify need to get their mortgages elsewhere.