Spring MVC with JBoss vs Tomcat - Advantages / Practice

Okay. This is again a question of industry practice.

• Tomcat = Web Container
• JBoss, WebLogic, etc = Application Servers that have Web Container within (for JBoss, its forked Tomcat)

Spring does not need Application Server like JBoss. If we use enterprise services like JMS, etc we can use independent systems like RabbitMQ, ApacheMQ, etc.

1. Question is why do people still use JBoss and other Application Serves for purely spring based applications?
2. What are the advantages Spring can make use of, by using Application Servers? Like object pooling? What specific advantages does Application Server offers? How are those configured?
3. If not for spring, for what other purposes Application Servers are used for Spring/Hibernate, etc stack? (Use cases)