IMO learning and knowing hobo signs is a worthwhile pursuit. as previously mentioned being able to leave universal signs behind so any who happen to follow are apprised of danger seems to be helpful, especially if you are the one following. but there is another way i look at it. humans, being squirrelly, would leave false marks, or obliterate marks, or change them. If you could get a good hot meal from a specific home, would you want to share that resource with every other person behind you? or perhaps maybe keep others away so they will have food to share when you are there?

or possibly leave a sign for a good meal that leads into a mine field?

i am thinking that, as has already been implemented, if i leave a sign behind, its for my family. basically a code that they understand but not general knowledge. each family member has a sign, either carved or something out of place. think of "My side of the mountain" an acorn on a rock to most means nothing, but if its not around an oak tree it can. thats the basic notion.

lastly, i know that its not fool-proof but it works. hunting for mushrooms on public land me and mine communicate in this manner. even with other people around.