Because a pluggable architecture translates into flexibility, extensibility and maintainability.
Apache Hop is focused on increasing flexibility and all the components in the platform should be pluggable.
As a developer, this makes it easy to add new functionality. As a system administrator, it gives you full control over the functionality you want to allow in your systems, as a data designer, it gives you full control to pick and choose the functionality you want to use.
Hop is built around an ecosystem of plugins, this gives the end users and infrastructure team the ability to create a custom version of HOP tailored to the project or company needs.
The most important plugin types are the following 4: