it's also about the level of control over what is happening. If the declaration of an object/variable automatically calls a constructor e.g. if

Person somePerson; 

was automatically the same as

Person somePerson = new Person(blah, blah..); 

then you'd never be able to use (for example) static factory methods to instantiate objects rather than default constructors i.e. there are times when you don't want to call a constructor for a new object instance.

This example is explained in Bloch's "Effective Java" (Item 1 ironically enough!)

It's also about the level of control over what is happening. If the declaration of an object/variable automatically calls a constructor, for example, if

Person somePerson; 

was automatically the same as

Person somePerson = new Person(blah, blah..); 

then you'd never be able to use (for example) static factory methods to instantiate objects rather than default constructors, that is, there are times when you don't want to call a constructor for a new object instance.

This example is explained in Joshua Bloch's Effective Java (Item 1 ironically enough!)