I typically trailer to wherever I am going, so I'm not usually hundreds if not thousands of miles away like others in the community. I love driving my Jeep out of the state to wheel, because I like the adventure, but my wife can't handle it, so I compromise to keep her happy. Maybe out of ignorance, I don't carry another Jeep worth of spares in my Jeep when I am on the trail. For those who have wheeled with me, I'm the first one with tools or recovery gear when someone has a problem and glad to get my hands dirty if I can help.
My thought was to take a spare regardless. My trips are my yearly vacations, and I wouldn't want to have my vacation cut short because I don't have something as silly as a spare, nor can I rely on finding a 40 in some remote location should I sidewall one. Having said that, I try to bring trip ending spares back at my truck. If I'm with a group, it would make sense to me that we plan out in advance who carries what to maximize the chances that everyone gets out. In other words it doesn't make sense that multiple people carry spare rubi axle shafts and no one carry a steering box. Just an example, but you get the idea.
I constantly think about maximizing efficiency and tend to over build, not because I'm doing the hardest trails out there, but because I want to minimize my chances of breaking. Weight increases stress on all systems and makes it harder to climto and weight outside the axles is even worse. Maybe it's just an engineer OCD thing, or being a cheap assist, but I don't want to spend another $1000 on an upgraded / heavier tire carrier than I already have to move more weight further behind the axle. Not that I won't, I would prefer not to if I don't have to.
Anyway, I hope that adds color to the conversation, so before this thread gets any more off track, let's talk spare in the back of the cab. It may be as simple as it doesn't fit - end of conversation, but I couldn't find a whole lot on the subject last night when I was searching.