The developers of browsers have been at least two reasons to abandon the Java plug-in browsers.
The first reason is the pain, from the continual appearance of new security holes in Java, making the browser more vulnerable.
The second reason is the developers dream about creating a universal format websites, compatible with mobile and desktop browsers. Since mobile web browsers don’t support Java plug-ins, it is possible to implement the same functions for different browsers sometimes had two different ways.
Since Chrome and Firefox have already abandoned the use of NPAPI Java plug-in, make sense to support it in Oracle do not see, and announced that in September its development will be discontinued.