It is very natural to see the attitude of the 'rulers'. If you see the people who currently stay and rule the city it should be very easy to understand why this approach.
These people come to Mumbai only to earn money and become wealthy. None of them care about the city. If you grow up in the city and plan to be part of the city then you may care about the city. What does our CM or most of his cabinet ministers care about the city. They care only about personal wealth. Also our central govt cares nothing about the city as long as it keeps contributing to the national wealth.
So just dividing the city in different administrative parts will not help. more drastic and demanding approach by the city residents is required