Most of the software-industries are focused on the performance of their software instead of the popularity of the users with low-performance PCs. Eclipse became popular after 2014, and it was one of the widely used Android app development IDE before Android Studio became popular.

just trying to contribute).Eclipse is one of the powerful IDE tool available for Java and various other programming languages such as C, C++ and web-based scripting and programming languages. then the chances are you will be downloading the JARs for Eclipse pluse an x86 implementation of the libraries that drive X-Windows for SWT. but you also get the distributions compiled files that are the implementation of SWT for that platform. that means that it is a binary distribution meaning you get the JAR files which are indeed pure Java. when one downloads an Eclipse distribution, notice that one downloads a distribution for a specific platform. this results in the best possible UI performance on a given platform.

So on Windows, they map to WIN32 UI and on a Mac to native MAC UI and I guess on Linux to X-Windows API calls. However, when Java invokes the classes and methods that are SWT, those are in fact mapped to native OS UI functions. SWT is the 'Standard Widget Toolkit' that provides a Java accessible UI that includes buttons, windows, font control and all the other items that are needed to build a UI. As such, a new UI technology was introduced called SWT. When Eclipse was written, it was found that attempting to achieve both the performance and desired 'look and feel' was not achievable through either Java UI at the time (AWT and/or SWING). If we delve a little deeper, we will find that the biggest one here is the UI functions. As such, Eclipse is not 100% Java but instead contains C code that assumes specific environmental components. This is because they make assumptions about the platform on which they run. It is my understanding that there are portions of the Eclipse project that are platform dependent.

Eclipse for ee developers