People love loud sounds and lights, be it explosions, light shows, loud music, automobiles, and a myriad of other things, what can I say? It's a form of group stimulation that for whatever reason cultures find acceptable.
I don't launch fireworks, and I agree people should be much more considerate about it, and keep loud sounds to specific pre-arranged times like 11pm to 1am for midnight events like New Year, 9pm-12am for other events. It's not so bad if you can expect it, but it's the random intermittency through the whole night is what I think is the most harmful thing about it. ANC headphones is the opt-out.