This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
Because it isn't accessing a private variable. It's accessing a public method, and that method happens to return (a copy of) the value held by the private variable. This is one of the points of encapsulation - you can expose values when you want, but in a controlled way.