The most accurate response to why many organizations stick to using legacy systems over replacing them would be:
Organizations do not want to disrupt their ongoing processes, so they do not bother modernizing their software.
This response highlights the concern for stability and continuity in operational processes, which is a significant factor for organizations when considering whether to transition to newer systems. The risks associated with transitioning, such as potential downtime, the need for retraining staff, and the possibility of losing data or requiring significant adjustments, often lead organizations to retain legacy systems.