Every single site that runs on Mediawiki that I have ever visited has the option of replacing the title of an article with the following phrase in the url:?&curid=[any number]. For example: http://rationalwiki.org/wiki/?&curid=1999, https://en.m.wikipedia.org/w/index.php?&curid=2001
So, since PMWiki is wiki software like MediaWiki and has a url structure that is similar to Mediawiki, why don't pmwiki site urls have any kind of ID system?