The question that gives the Moirai their weight is whether the gods can overrule them, and Atropos is where that question becomes concrete, because her act is the only irreversible one of the three. Homer puts the case at its sharpest in the Iliad, where Zeus watches his son Sarpedon go toward his death and considers lifting him out of the fighting. Hera answers that he may do it if he wishes, but that no other god will approve of a man long due to his portion being released from it. Zeus lets him die. The passage neither denies that he could have acted nor lets him act, and antiquity never resolved it.
Hesiod records the same ambivalence structurally rather than in a scene. The Theogony names the three twice with two different parentages, once as daughters of Night alongside Doom and Retribution, once as daughters of Zeus and Themis and sisters of the Seasons, with Zeus giving them their honour. Both readings stayed available: fate as older than the gods and standing outside them, or fate as the ruling god's own ordinance.
Cult reflects that awkwardness by staying small. The Moirai receive offerings at births and marriages, at shrines shared with other powers, and they very rarely hold a large civic festival of their own. A city organises worship around outcomes it hopes to influence, and Atropos is the name Greek religion gave to the part of the arrangement that no amount of organisation reaches.