I am curious why SE or game developers in general (assumption) don't update "old" content as a game evolves. That is, periodic updating of pre-existing content to make it slightly different/more challenging so it remains challenging and rewarding.

Take the faction NMs for example. Why don't they add a layer of complexity or different piece of gear to these fights every now-and-again to give players a reason to revisit these fights?

By the time I reach 50, the only thing relevant to me, or really able to get people for, will probably be the latest and greatest Primal fight. To me, it is a waste of work not to add small pieces to old content to refresh it and make it different or new.

What are all your thoughts?