[mping]

Besides all the historical reasons cited, there's a simple reason: economics. The bulk of enterprise software are CRUD apps that maybe chat with an ESB or whatever; the quality is mediocre/ok, and whoever pays the bills just want to get the project done ASAP. The pool of Java devs is HUGE, it's quite easy to lose a Java dev and get him replaced the day after. The risk of using Java is very low from a management perspective; if you replace Java with Ruby/Scala/Python/etc the perceived risk would be much higher.

Besides, most big enterprises are already paying IBM/Oracle/Jboss/etc for Websphere/MQ/ or whatever App Server and support; it makes sense to use it anyway.

I would say it's mainly inertian and (perceived) risk management. BTW, I believe the Java camp got alot of things right, but that's another story.