Some call it airmanship.......
I believe that the thought behind turning the landing lights on below 10,000' was two-fold.
The first is to make the aircraft visible to other aircraft in the radar vectoring area/terminal area, whatever you may call it. It is possibly of slightly less usefulness these days with the advent of new generation ACAS systems but nonetheless, on a personal note gives me a warm feeling that I can confirm the position of the aircraft in conjunction with the ACAS display.
The second is detailed in an Airbus operational briefing notes here:
http://www.airbus.com/fileadmin/medi..._ENV-SEQ05.pdf
It has always been for that reason that I have left them on until, and turned them on at, 10,000'.
For all the good reasons that have been pointed out already, turning them off a times is prudent too.
Hope this helps.