You’re submitting your bills by mail. First, handling, managing, and mailing paper billing is time consuming, resource wasteful, and expensive. Second, unless you use USPS Certified Mail (more expensive option) – you do not know if the insurer ever received your bill or whether they received it timely. So you wait and hope you receive payment soon. If not, you spend (waste) time and resources following up or submitting a duplicate bill. If timeliness issues come up pertaining to statutory or regulatory guidelines, you have no proof of your billing submission or the actual timing of its delivery.