V來/去1 is the bare single tag: toward me or away from me, nothing else. 趨向補語 stacks a path-shape first (起/出/上/下) and only then 來/去, so it also says up, out, or back.
Standalone 去 is the main verb 'to go' and takes a place (去學校). Here 來/去 sit behind another verb and only mark its direction (跑去學校).
wrong reference point: 我在家,請你拿去 (you're handing it to me) → 我在家,請你拿來
place before the tag: 他跑學校去了 → 他跑去學校了
dropping the verb's own meaning: 他來學校 (only 'comes') → 他跑來學校 (runs, and toward me)
English 'come/go' are full verbs; learners use them alone and forget to keep the real action verb in front (跑去, 拿來), and they pick toward/away by the listener instead of by the speaker.