There are advantages to not looking inside the object's box. For a start,  most people work more quickly with visual representations of a program, than they do by reading and entering text.

Secondly, people are not generally tempted you to directly modify that object. If they did, they would be tampering with the details of how the object works. Now this may not be a problem generally, but suppose the person who programmed the object in the first place decided later on to change some details? Suppose then, that you downloaded these updates. Now you would be in trouble...(don't you just love these disaster scenarios?) your software would no longer work correctly! But, so long as you just deal with objects as boxes via their messages, the software is guaranteed to work.

Why all this concern for being able to change software? Well,  software often does change (is 'updated') over time. A popular saying is that "software is not written, it is re-written". Costly mistakes can occur when software breaks (malfunctions) because someone tries to change it. By using 'objects', the user is less tempted to create change.

To read some more complicated stuff about objects, click Objects Part C