Chucking smoldering clods of gunpowder into the sky with a mortar and having them explosively disperse incandescent shards of metal is lots more amusing when you're standing about 300 yards from the launch site, rather than a mile away, and thus the detonations are above you (where they are concussive and enveloping) instead of on the horizon (where they are a pretty particle-driven screensaver with a poorly-synchronized audio track).
Also, being a fireworks technician looks like fun. Wandering around mortar tubes stoked with what can only be black powder (judging from the gouts of white smoke issuing from them on ignition) must be a treat for the olfactory and auditory senses. There's that ballistics stuff to fiddle with, too - bomb of weight X propelled at angle Y from mortar tube of caliber Z and backed with A mass of powder. And safety concerns, but bollocks to that.
Happy Fourth of July.