Everyone is going to have different needs. My truck has no 12V wire on the system. I have never come across a need for it. My trailer is plugged in when at home and it is plugged in when I get to the campground. We never camp more than 25 miles from home, so I have no need to run the fridge on gas or anything else on battery power for that matter.
If your truck already has one, I wouldnt remove it or pull a fuse to disable it. Eventually I will probably add one to my truck but so far in the 4 years that I have owned this truck I have not had a need for it.
