It doesn't install the extensions by default because you never, ever want a
program to install or change settings that tie into your web server. The
process could wreak havoc on an IIS installation that has been set just the
way you like it then the FP Server Extensions come along and do their own
thing. IIS Add-ins and extensions need to be installed manually so that the
developer, or server administrator, is only installing features that they
need and also to have a chance to backup the IIS metabase and settings
before installing an add-in or extension and restore the configurations if
necessary upon a failed or misbehaving install.