Many pages don’t render correctly when printed to PDF (it’s easy to accidentally make your page entirely illegible after printing), and most pages that rely on JavaScript completely fail to operate when saved as a web archive. So saving pages is, in my experience, quite a crapshoot.
In addition to that point /static/ content on websites can be easily cached.
Want to have a forum as an optional /extra/ on an otherwise static page? Maybe OK, but please have a way of getting that forum as a different page (which is updated on some basis, maybe per post, maybe with a cooldown of maximum 1 generation every X or only during low server load, etc).
