Fireworks displays are associated with long lines and waits. If only you could take your bike there, but maybe you don’t want to bike downtown. It makes much more sense to subway/drive to a convenient spot, hop on a ridesharing bike, and redock it shortly before the fireworks. Then ride to a prime location, yes you’ll get a few dollars overtime charge, redock it after fireworks over, and ride back to the subway/car before final docking.
Very simple, save yourself an hour+ of time and risk of pickpockets when walking in a crushing crowd or subway near event.