Especially for small and mid-sized companies, project management software is not always an optimal solution. In addition to the cost of software licensing, there are costs for installation, configuration, and long-term maintenance of the software and hardware (server).
In contrast, Software as a Service (SaaS) is simpler. With SaaS, software is not purchased outright, but used as-needed, with costs incurred on a pay-as-you-go subscription basis.