Lets say the limitation of 3 days for shinobi feast doesn't help. I still don't understand why they don't just let it be there for the whole week.

I'm one of those rushers praiseluka talked about because, due to the limited time of the event i wasn't sure to be able to complete it within the end of Saturday, if lasted until Wednesday i would have had no problems in just getting 5 wins yesterday and the other 10 in the second half of the event.