While I agree with this, it would be counter-intuitive to delete retrospectively learned skills.
I mean, really, would you have the next patch with a bunch of R50s all with no skills farming the same NMs for the best skills and spells, or have them all bought from a shop? What would be the point in that other than remove gil from the system?
I like the idea, I have to say, although it would be an impossibility.