Sure, but is there an advantage to bonus IP for winning X games for X>1, compared to getting bonus IP for the first win?
First win of the day is an 'easy' task psychologically, so people get conditioned to always come on and play at least one game for their win of the day, even if they're busy. Getting like 5 wins or 10 wins can feel like a chore, so people may not feel compelled to even try on a given day, and maybe just skip league on busy days and just grind it out on a weekend or something, if they even care at all. Special goals to work towards might be fine for people with certain mindsets/lifestyles, but a single win of the day is prone to be easy enough to hook everyone from the working parents who only have time for 1 game, to students on holidays with no other responsibilities who can play 10 hours a day.
I feel like first win of the day is probably more reliable IP than even a big chunk of bonus ip for a batch of wins, so more 'contract' types would be needed, and for the reason I said initially there aren't very many that wouldn't inadvertently promote weird play and so be a no no.