Karachi is the largest and most dense city by a significant margin, so its needs are much greater.
In comparison, Lahore, the second largest city in the country, and the premier city of the affluent province of Punjab hosts far better infrastructure. Consequently, it suffers a mere fraction of the magnitude of such issues as Karachi. In addition to a different geography, which, of course, is a significant factor, Lahore has received much greater investment of political will, civic planning and funds.