The reason accessors are a code smell is that OO programming is supposed to be about objects performing tasks that they know how to do, not programmers fiddling with the objects' internal states. The internal states should primarily change as a result of interacting with their universe. If that's not the case, then maybe OO is the wrong approach.

That is not to say that there should be no public accessors in good OO code. Code smell is not an absolute condemnation, it's just a marker that should make you think twice.