Lighthouse keeper why have done away with the light house keeper for ?

This does not belong in Zoology but the first part of your question should have told you why... you said "system of lamps and lenses or in older times from a fire". That of course requires constant care thus the need for a person to stay close by. Even though the lighthouses are the exact same lighthouses as back then they have updated the insides with modern technology. With the use of electricity there is no need for someone to always be there. They can be turned on and controlled from miles if not cities away. Of course someone has to go in from time to time to clean and or make repairs/updates. But it does not require 24/7 attention.