Never said i was. Just I thought it was one of the main rules. There isn't much more annoying then clicking on a link just to find out it is still under construction.
And what then. You moan more cause there isn't something there saying what's going on.
If a vital system was being replaced or something then Under Construction pages would be requird. OR if a site hasn't actually launched then what? Just leave it to give 404/403 errors until you put the index page up.
Who'd be linking to it. A user may have heard of it somehow and gone along. It may have been picked up by a search engine OR linked to in a forum as something to watch. There area plenty of possibilities that justify construction pages.