Dead shows were each unique because the band did so much improvisation, in fact, they didn't even follow a set list. you never heard the same show twice. for instance, if you saw them three straight nights, they would probably not repeat a song. Sometimes a show might pretty much suck, but the next night it would just be transcendant.
the Deadheads were like a tribe, you would see your friends, say, in Wisconsin where I used to see them often at Alpine Valley, and then maybe again in Philly...and then there was the chemical enhancement. I knew a number of guys in college who would hit the dead tour just to score enough drugs to sell back on campus to fund that semester's partying. 'Heads would show up hours ahead of time just to find their friends, and party like hell before the show started.
plus it seemed there were always just great looking women.
the only jam bands which remotely move me like the Dead used to are Moe and Govt. Mule.