Beating a dead horse

Beating a dead horse seems to be a fun activity people do it all the time everywhere. There is not a seconds hesitation to revive a discussion which has been long dead. For me personally I compare it to beating a Piñata for ten hours and still not being done, sure at first its new and fun you get to beat with a stick on this horse like (or other animal likeness) object thats hanging down, but after ten minutes you begin to wonder what really is in there yet you can't crack that darned shell, two hours later you begin cursing and just want that damned thing to open so that you can have those sweets that are supposed to be hidden in there. After five hours you are frustrated maybe a bit tired and have stopped cursing two hours ago, but you don't stop because now you don't want to waste those previous five hours, at ten you finally breach the Piñata's hard shell and find absolutly nothing because this Piñata had a very thick skin and thus no space for sweets.
All that the beating of the dead horse can bring is the same as this Piñata which would be a waste of time and energy as well as the often occurring frustration which appears at the end of such a futile act.
So why in god's name would you ever want to engage in something that you know will only result in those things and end up with the same or similar conclusion as the one previously available?