I agree with your grandfather, but not so much with the other things you say...
The problem with a Bic lighter is that if the fire is difficult to start, the lighter metal parts heat up and begin to melt the plastic in the lighter. Then it doesn't work. Ask me how I know.
You really think a first aid kit is not necessary for multi-day hikes? Bad advice and wishful thinking, according to somebody whose life was once saved with a first aid kit. If you do enough stuff, in remote enough areas, sooner or later...
Filter rain water? Why? Pretty pure stuff.
Updated list of the earliest "10 Essentials." There is a real potential need of whatever item is the best available today. Ultimately, it is mostly about what is between one's ears and in one's heart.
solid platform to start with THX