In-house billing is expensive for a doctor's office. They're paying hourly wages, benefits, vacation pay, workers’ compensation insurance, and more. Moreover, it’s not lost on them that a person earning a percentage of the revenue collected is going to work harder than an hourly wage employee who is getting a paycheck no matter how much they collect in a day. Doctors know it is most cost-effective and in their interests to outsource to a medical billing business.