The default access is otherwise known as package level private or protected... your choice, it doesn't really have a term, but its useful to think of it that way.
If you dig within the source for
java.lang you will often see it - allowing other classes within java lang to be able to access some of the internals of this class without exposing those internals to all of the world.
Just glancing, an example of this is the
java.lang.Integer (grepcode) that allows there to be a single point where this information is stored. As this is associated with
stringSize (just below it) that is likely used within
java.lang.String it means that one doesn't have to have two copies of it or expose it. Other methods in the area also show more of this Integer/String relationship.
Thinking about this more, you've got
Integer.toString(int i) and
String.valueOf(int i) - both of which do very similar things. While its debatable if you want to have the ability to do the same thing in two classes... if you do, you only want to have the code in one place - which again points you to having a package level encapsulation.
Putting things within the same package is supposed to be an important part of encapsulation. The classes within a package are supposed to work closely with each other. It means these classes should be able to look at each other's internals and work with them. It avoids having
java.lang.FunkyStringConstatns sitting out there for all the world to see... and once the world sees it as something public, it means that one can't go and change it.
This has less meaning when one works on the entire project from start to finish and there is no public API. Its more a 'yea, its there' then. But if you are working on public APIs, you will want times to be able to share data without sharing it with the world.