It's debatable whether or not the OP even accurately describes medieval life. Apparently there is some confusion about where charcoal comes from or what the principle fuel of ironworking was in the medieval period. Understanding actual medieval life, conditions and technology, IMO, is an important part of this reasoning, and IMO the OP is not convincing in this area - as others have described. There are also issues of the frequency and fatality of spider bites, whether or not rattlesnakes and elves share the same habitat - etc.
Secondly, and just as importantly, is the relevance that this would have to a fantasy species anyway. Elves are not the same as humans, biologically or culturally. I think you're inferring too much from the similarity of the rules governing PC humans and PC elves. For example, I'm not convinced that elves are allergic to poison ivy - some humans aren't even - so why would you list that in a list of the hazards of the forest facing elves?
Why would you expect the DnD Players Handbook to enumerate the thousands of cultural details that would explain why elves live in the forest? Does the PHB have to tell you that elves are immune to poison ivy? Doesn't it seem reasonable was that their approach is to assume that elves live there, and have whatever technological and social requirements are needed? I don't think it would take any sort of extraordinary magic to live in the forest.
Also, in terms of culture you also assume that humans learn skills, spells, classes, etc. as easily as elves. This may be true for PCs, but again, I think you infer too much from the PHB. IMO the PHB is not a manual for campaign world simulation. If a player wants to be a wizard, he simply makes one up. But this does not have to be the case for NPCs! An NPC would have to have a background to make the opportunity of being a wizard available. Certain cultures are good at certain things because of a history of supporting the activity - elves could produce more wizards than normal simply because their culture prioritizes taking care of spell books, study, etc. The PHB rules are not going to deal with this issue - it's irrelevant from the point of the players, who are assumed to be able to play whatever character type they want.
Secondly, and just as importantly, is the relevance that this would have to a fantasy species anyway. Elves are not the same as humans, biologically or culturally. I think you're inferring too much from the similarity of the rules governing PC humans and PC elves. For example, I'm not convinced that elves are allergic to poison ivy - some humans aren't even - so why would you list that in a list of the hazards of the forest facing elves?
Why would you expect the DnD Players Handbook to enumerate the thousands of cultural details that would explain why elves live in the forest? Does the PHB have to tell you that elves are immune to poison ivy? Doesn't it seem reasonable was that their approach is to assume that elves live there, and have whatever technological and social requirements are needed? I don't think it would take any sort of extraordinary magic to live in the forest.
Also, in terms of culture you also assume that humans learn skills, spells, classes, etc. as easily as elves. This may be true for PCs, but again, I think you infer too much from the PHB. IMO the PHB is not a manual for campaign world simulation. If a player wants to be a wizard, he simply makes one up. But this does not have to be the case for NPCs! An NPC would have to have a background to make the opportunity of being a wizard available. Certain cultures are good at certain things because of a history of supporting the activity - elves could produce more wizards than normal simply because their culture prioritizes taking care of spell books, study, etc. The PHB rules are not going to deal with this issue - it's irrelevant from the point of the players, who are assumed to be able to play whatever character type they want.