Why restart required for deploying Ext plugins?

What happens during the deployment of Ext under hood. It's not same as what happens when other plugins deployed.Let's have a look.Before that please go thorough the Anatomy of Ext to get clear idea
The deploy process creates

1. ext-impl.jar from the compiled code of ext-impl/src - if  you customize the impl classes
2. ext-service.jar from the compiled code of ext-service/src - if you customize the service classes
3. ext-util*.jar from the ext-util-* source folders - if you customize the tag library or utility
4. Now the deployer starts to copy jars to Liferay's WEB-INF/lib
5. Before that the first step is deploy portal-*.properties and systeam-*.properties files to Liferay's WEB-INF/classes
6. At last not but least copies ext-web folder into the deployed liferay's folder
7. Here i am not using ant for build process so the work done by deployer. If you are using ant you can use ant-deploy(war will be created then manually copy into Liferay deploy folder) and ant direct-deploy(Ext plugin is directly copy to the running Liferay instance and will restart).

Hope you understand why you need to restart the server.