clicks-as-votes isn't new. There are many reasons for the last click though.

   1. found what you want
   2. got bored
   3. tried a new search term
   4. browser crashed
   5. continued your searching session through the site (ie going forward not back)
   6. tab based browsing

It's true that you wouldn't keep searching after you found what you want, but that does not necessarily imply that if you stop searching you have found what you were looking for.

Alternative search engines have tried and died.