I use to plunder and i can tell you that the main reason why the Plunder system is so unfriendly is because when you accept to Plunder once then you are COMPELLED to plunder again also for the other two daily attempts.

I'm one of the people that after 1 succesful SS plunder attempt would gladly go running the other two attempts as convoy attempts, if was possible, to not be compelled in staying there for 30-40 minutes by clicking refresh hoping to see two more SS convoys that I'm able to claim before my rivals do it in my place.