ISO certification is mandatory for many organizations because it helps them to demonstrate their commitment to quality, continuous improvement, and customer satisfaction. It also helps organizations to gain the trust of customers and suppliers, as well as access to new markets. ISO certification is also a good way to show potential customers and partners that your organization is serious about its quality management processes. 

The eligibility criteria for ISO certification usually depends on the type of certification being sought. Generally, the criteria will include having an effective quality management system in place to meet the requirements of the ISO standard, a documented process for continual improvement, a process for monitoring and measuring performance, a system for collecting and analyzing customer feedback, and a plan for corrective action. Additionally, most ISO certifications require regular audits and reviews to ensure that the standards are being maintained.