If everyone in the world required about two hundred square metres for their house, the entire ocean even if occupied, there will not adequate land. Then where will they stay? Place like New York, Singapore, Bombay and other such metros have very high population.
The stair lifts are specially meant for the multi storied buildings. There will be a comfortable chair attached to one side of the railing. This is done with utmost care and precaution. It is remote operated. The chair goes up till the place we require. This permission is mostly for aged who suffers from arthritis and cannot go up because the knees do not permit. It is the suggestion of the orthopaedician to utilise such device while travelling by.
There will be some aged people who have no alternate other than having a stairlift. Every house may have someone who requires this privilege. If there is any technical hitch, it automatically gets disconnected and the man travelling is absolutely safe.