In case of web applications, why java is also called platform independent?

In case of desktop applications, it is clear that Java is a platform independent, because you do not need to compile the java desktop application on each OS to run appropriately.. it is enough to have a JVM installed on the targeted OS, to run the application.

But I can not see that concept clearly in case of web applications, because if you want to run a web that developed in Java programming language, you need a JDK installed in the server and an apache (especially Tomcat) web server, and once the web is created, it will stay on the server and it will be requested with a client web browser. This is the opposite of the previous case (desktop applications), in which each client must obtain a .jar file to run the java application (independently of his OS).

So where is the irony? And how can we benefit from the platform-independent issue in that case?