They have AK 47s, if that can survive so can a document. Or nikolas teslas skull.The UN document didn't survive into the 10th Millennium never mind the 30th like we are now. Never mind the fact that it's not particularly impactful or well known right now and it's not going to get anymore either of those things as time goes on. There's only so often you can completely ignore the tenants of a document every time there's a famine, drought or a disease that you can consider it important or true nomads have to make really difficult decisions about the compositions and future of
The actual fundamental rights are not impactful, but the fact that humans have certian fundamental right is incredibly impactful. Like even most dictators don't just excute people these days because they have to pay lip service to human rights of any dissidents. Like calling not impactful is not accurate.
Individual rights are easier to ignore but things like right to life are very impactful.
Also its even more important for desert nomads, because ir signfies to them how far they have fallen.