It’s curious that people who are hiring put so much faith in resumes: a resume is a document made by the most biased source possible. Whereas a recommendation, if from a trusted source, knows both parties and, even if biased, has conflicting biases. As much as they might want to get a friend a job, they want to protect their reputation. They’re unlikely to recommend someone who doesn’t live up to their billing.
Unless the job you’re hiring for is to be interviewed all day long, most interviews don’t tell you very much about how the person will perform when actually working. A recommendation on work done at another job in a similiar role has to weigh more heavily than their ability to merely talk about that work.
Of course resumes and recommendations are not mutually exclusive, but one is given undue dominance over the entire process.