Web services ensure that you can handle data from your own and other systems in real-time. The ESB can handle large quantities, delivers extreme performance and buffers (cached) the data so that the web service always delivers! So even if web services of underlying IT systems are equally slow (or not working), the ESB takes care of the data in real-time.
The most important function of an ESB is that it distributes data from one system to another. To achieve this, the data is first transformed so that it is suitable for the system. When you as an organization receive a purchase order, the ESB ensures that it is converted to your own purchasing system so that you no longer have to enter it manually.
Systems age, but often still play a core role in the organization. The environment and desired digitization place new demands on technology. There are more and more integrations between systems and interdependence is increasing. What happens if integration is not successful? Do you want to guarantee the continuity of your organization, better control your IT costs and be ready for the future? A simplified IT infrastructure and architecture is a precondition for this.