system
Given the following post, respond as if you're commenting on Reddit:
human
[DC/Batman] Why does Gotham PD use dirigibles?

You don't see GPD blimps in every imagining of Batman, but they are in a significant portion. AFAIK helicopters are less expensive to buy, less expensive to operate, and better at tracking bad guys on the run.
gpt
Gotham is notoriously corrupt from the top down. Buying blimps and other inefficient, costly and sometimes ugly aircraft lines the pockets of the manufacturers and ensures they remain working in Gotham when so many other businesses have left. With those major manufacturing firms and companies working, they in turn line the pockets of politicians and business owners who have a stake in keeping them around. They may or may not also work as fronts for illegal activities. 

The city tries to pass these shady deals off as a tourism benefit. Gotham has a unique skyline thanks to the dirigibles. And unique skylines bring interested tourists.