With mortgage rates at unprecedented lows, why are more people not taking advantage of them to refinance or buy houses? The answers are complex and include sagging consumer confidence in the economy and high unemployment rates. But some mortgage lenders point to what they see as overreactions within their own industry that are discouraging and disqualifying potential borrowers — sharply increased credit score requirements, higher down payments and add-on fees imposed by mortgage giants Fannie Mae and Freddie Mac, which control about two-thirds of the loan volume. The most controversial Fannie-Freddie fees, which were introduced as the housing bubble began deflating, are known in the industry as “loan-level pricing adjustments.” Many mortgage executives say they are excessive, given the stricter underwriting standards now in place that reduce the long-term risk of new loans being originated today.