We turn them on through 10,000'
How things have changed throughout the years. Landing lights were designed for night use. To be switched on just before rolling on the take off run and switched off within seconds of landing gear retraction. One of the reasons for early switching off after lift off was to minimise the blinding reflection entering cloud and distracting the crew. Modern pilots obviously are not affected by lights reflecting back into the cockpit. That is a good thing.
For landing, the landing lights were turned on at 200 feet just before crossing the threshold. They were used to illuminate the runway surface. To aid judgement of flare height. To illuminate drunks or animals on the runway. In fog or mist the landing lights were off for landing to prevent being blinded momentarily if the aircraft was passing through ground fog patches. Pilots were taught to be able to land without the aid of landing lights because landing lights can go u/s. The life of the light globes were based upon the above rate of usage.
In later years, someone thought it would be a Good Thing to turn on the lights below 10,000 ft regardless of being a bright sunny day or a pitch black night in cloud. Ooh! look, sez observers on the ground - I can see aeroplane lights high in the sky. Aren't they luverly? They are certainly no help to pilots at 10,000 ft...
Already, airliners are festooned with strobes, tail advertising logo lights and passenger window lights. Seems an overkill having landing lights all over the sky below 10,000 ft.