In the calendar tool, the ical link is rendered as a clickable link. Normally the OS has a handler registered and automatically opens the calendar app, such as Calendar.app on OSX or Outlook on Windows.
Of course, Outlook does not embed the calendar correctly (events are not updated in the past but rather imported as a copy, and worse, the timezone is mixed up, no more support for time saving zone).
Thus, the link method will be abandoned. Users should always copy and paste the feed manually by using the menu options in their calendar tool