WebApplicationInitializer not loading

I followed following link to create tomcat server and now its running fine.

http://websystique.com/misc/how-to-setup-tomcat-with-eclipse/

If anyone can explain how this is different than simply creating a tomcat server and running it without modifying Location etc..?

Update:

It turns out that after you update pom.xml and update maven project, eclipse removes maven dependencies from classpath ... adding them again is the right solution.