That is very true. There should be an escape route always. In malls and big buildings, we see steps also in addition to lifts. These steps are useful for people to escape during emergencies. In case of any fire in these buildings, power will be stopped and lifts will not work. So people will use the steps way to come out of the building, As mentioned by you it will be good if the apartments also are provided with two exits like independent houses people will have two ways to get out of the house. I have seen some flats where there are two doors to go outside. But the majority of the apartments will have a single door only to go out. All apartments will have a common area on one side of their apartment only and that common area will have lifts and stair cases. If we have to provide two doors, the second door also will come to the same common area. Otherwise, the common area will increase and that will make the cost of the apartment to go up.