Due to the lore, I've found an interesting topic surfaced by theory. A theory that the "true Humans" do not respect, support, nor accept the Guardians as their protectors.
Update: I forgot to include that there are some forms of Information referring to Guardians such as Saint - 14, whom was actually much respected and loved by the people of The Last City, but due to his obsession with the downing of the Fallen through a long crusade, he is no longer commonly mentioned, but only as a legend now.
Nevertheless, we've gotten some pretty good feedback regarding as to why. Maybe the "living Humans" see us as something tyrannical?
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Guardians are somewhat immortal, and they were once dead. That would disturb any regular human being. On top of that, they were also given superhuman abilities and can be brought back from the dead. What's stopping them from creating a tyrannical government?