Simple: Because the algorithm is flawed. I played a 20-minute game and got 205 IP. You get exactly the same for a 7-minute game. I don't think it needs any more explaination. Also, I still have no idea why does it have to be party IP weekend. Why can't we all just get bonus IP without having to look for a party?
Also, because someone had this stupid idea that you only get bonus IP if you play in a party, people are forced to play with basicly anyone they find, resulting in totally uneven teams with players from bronze to diamond (or maybe even higher). This makes stomp games much more common, which last 20 minutes and make you ask yourself a question "Why would I waste 20 minutes in a totally anti-fun match, when I can get the same amount of IP in 7 minutes?"
Also, I still have no idea why does it have to be party IP weekend. Why can't we all just get bonus IP without having to look for a party?
Because that wouldn't encourage players to play with their friends more... or at least to try to make new friends to play with. Which is the goal of the event.
