An object should have methods reflecting its external behavior. "Set your X value to 24" is rarely a nice reusable, maintainable external behavior.

People writing these kinds of objects generally haven't quite gotten in to "object thinking", and instead treat the object as a "smart record". Methods should instead be derived by understanding how the class might be used (including subclassing).

I think the Perl6 object approach where all variables are private to the class (and not even directly available to the subclasses) will make for some interesting designs, especially when thinking about reuse.