Contrary to what some think, A318/9/20/21 Ldg Lights do cause drag, vibration and fuel burn - they retract when "Off".
When was the last mid-air avoided by Landing Lights? We are also exhorted to land with Flap 3 by Mgmt, to save a similar single digit Kgs of fuel/sector. Try adding 10K to your landing speed, higher nose attitude, low thrust on approach and see some genuine safety implications to save a few Kgs
You can criticise all you like, but as shown above, it is fairly common practice to turn them off fairly quickly / only put them on quite late. Not just by pilot choice, but airline / manufacturer SOP.
NoD