As others have said, for me knowing a bit to avoid really yucky roads can mean avoiding an unpleasant day. This advice comes of course from having some unpleasant experiences, but depending on the area and such, winging it can be fun too. I generally like knowing where campgrounds are for the end of the day, and having only toured using maps, sometimes only locals can tell you that x road is used heavily by lumber or quarry trucks or whatever , so talking with people can really help when winging it.