License servers and downloadable content. Roughly 2005 is about the time when these started to become commonplace because developers began to assume always on Internet for applications that didn't have obvious network dependencies. So even if you have installation media, that media may not have everything needed and will likely not have patches for significant bugs that were discovered after it was pressed or the installer was downloaded. I think that's why the author picked 2005 as the cutoff point: prior to then, if you had the installation media / package, you could usually install and run it offline. Likewise, any subsequent updates could usually be downloaded 'outside' of the application and applied manually.
