You Ignore the fact that Islamabad & Delhi are not comparable.
Islamabad is a new planned city mostly resides by elites , politicians & bureaucrats with very less population with no industry or heavy traffic or huge population.
Btw , how do you control poor people from coming to Islamabad
Other side Delhi is one of the oldest city in the world with heavy population ( & more coming from another states regularly)
very large no. of vehicles, Industries, educational institutions, all political , Judicial, military, bureaucracy centre are here.
Every one lives in delhi, politicians, bureaucrats, elites, middle class or poor.
Delhi for everyone but it can't be said about Islamabad.
Our Chandigarh or Lawasa or more comparable to Islamabad.