See the part about support-costs in a different link.
But even more, I think it's "in the nature of programming" that for a given system you have some parts are regularly structured and externally visible but other parts that seem like they ought to be visible and changable from outside but which aren't and can't easily be made so.
This might be because they use intermediate variable or it might be because they have changed the implementation over time or for a variety of reasons.
And this ultimately comes down to the difference between the way intuitively you'd think X feature should be implemented and real, much-more-messy way X feature is actually implemented - the difference internals and an API.
Having internals and externals be equally easy to work with was the dream of the object orientation but sadly that has remained a fantasy and unfortunately looks like it will remain so.
But even more, I think it's "in the nature of programming" that for a given system you have some parts are regularly structured and externally visible but other parts that seem like they ought to be visible and changable from outside but which aren't and can't easily be made so.
This might be because they use intermediate variable or it might be because they have changed the implementation over time or for a variety of reasons.
And this ultimately comes down to the difference between the way intuitively you'd think X feature should be implemented and real, much-more-messy way X feature is actually implemented - the difference internals and an API.
Having internals and externals be equally easy to work with was the dream of the object orientation but sadly that has remained a fantasy and unfortunately looks like it will remain so.