Person radical on the left — the indexing semantic.
催 is to urge, hurry, press someone; the action is one person doing something to another, so the
亻 fits directly. Joins the human-interaction family:
促 (urge — near-synonym),
使 (cause),
仰 (look up to),
借 (borrow from) — all interpersonal verbs labeled by the person on the left.
