Do a search on successful ditchings, there have been many survivable landings on water. In fact a lot have happened close to land and near airports, a distance rule doesn't make much sense at all. If you can't swim a few metres offshore may be too far.
The high speed impacts make better viewing/drama for TV so tend to be focused on for ratings, nice graphics for effect etc...
I don't have any data on it but i would suggest that life jackets on aircraft have saved more than one person, and that outweighs any financial savings.