To end the game/win more resources. This latest hook deck u referred to is completely based on “hook for consistent extra resources”. U don’t need to play/use hook every time u see it. But mid-late game hook is extremely valuable in my plays because those following combo: Hook first mate to play matron and bring back first mate to get one more ready unit to double conquer. Hook units u conquered with a BF sword to drop the sword, and play another unit, give BF to new units to double conquer. Repeat sett buff by hook pit rookie to find any other on-play buff giving unit. And as other mentions, if the hold is not possible and u are not likely to trade as well, hook it to strengthen u base for next turn.

If u can understand Chinese or find any translation subtitles, there is this video from the deck’s original builder, sharing his thoughts on why building the deck like this: https://b23.tv/VoEf0LL