When I first read this I wondered why you would want to stick a candle into a soundboard.

Listen to the concert recordings of the same song. 10 concerts, 10 different renditions of what was called a song. That's because much of the time they were winging it which was their style and part of the attraction to catch as many shows as possible. :D

I always thought people considered them to be more cohesive as a band because they could follow each other, and explore so well ad lib.

I guess that depends on your view of what a band is and what they're supposed to do.
Having the ability to be able to jam well together doesn't make a tight band. Jamming gives the players a chance to try different chops with the riffs the others are playing. Some combinations work well, some don't. When they accumulate enough combinations that work well, those can be woven into a tune that cooks all the way through instead of high and low spots.
It's hard work and once it's completed, should be repeated the same way each time it's played. That's what makes a band tight.

The Dead took a different approach, developed their own style. They never wanted to be a tight band and to their credit they were successful at doing there own thing and keeping a loyal (read rabid :lol: ) fan base. I think their success was as much to do with the (counter)culture and lifestyle as the music.

There is plenty of room in music for all kinds of styles and variations. Unfortunately there is less leeway to be commercially viable.