Riot is missing a huge opportunity with the "Missions"

You implemented a mission system that only rewards during special events like champ releases. Why not just add a ton of big missions for each champion and give a small amount of ip or blue essence for completing them.. It'd be like an achievement system, and while the rewards for doing it wouldnt be great, the constant goal of collecting achievements would be awesome.

I feel like they were on the right track with missions, then stopped suddenly.