I will be brief.
Ever heard the statement "prepare for the worst"?
No matter how mild you think a trail is, there is almost always a chance to get badly hurt. If that happens, it is always better to have another truck close by. It doesn't matter if it is wheeling with you or just parked at the trail head. It's the possibility of those rare occurances that bite you.
For example...A buddy of mine in a super built rig was just playing around on some little hills. I MEAN LITTLE !! He was going slow, he had years of driving experience, he had been on the trail before, etc, etc. In some freak, twilight zone way, he rolled. People in the rig were not strapped in. It took 4 ambulances to get everyone to the hospital. Broken ribs, broken/dislocated shoulder, broken wrist, broken arm. The truck had to be rolled over using another truck, just to get everyone out. Fuel was spilling the entire time. It's that kind of impossible-to-happen situation that makes us all stress the fact of not going alone. Someone else was there to call the paramedics, and to lead them down to where the people were. If you are deep in a trail, and you are alone, and something happens, you have to either walk out of it or call someone that knows how to get to you. What if you were in a spot that you didn't have reception?
I know the people may have come out better if they had been strapped in. That is not the point I am trying to make. Its the fact that they didn't prepare properly because of the mild trail they were on and had been on before. This is worst case scenario stuff for sure. It could have been worse, and it could have been better. But....It could happen to you!
I told you I would be brief. You should see it when I get long winded. I am kinda passionate about this because I have a son that wheels his own truck. The only reason that I built the truck that I have is to be sure that I could recover my sons. When I worry about his well being, it is easy for me to get concerned about all others in the wheeling family.