In league there exists 2 kinds of players: those with 12 chests and those with 17 keys. Now, during every event, I see them selling key fragments and single keys, but no chests. And during this one, there are even 3 key options, but not a single option to buy a chest. i realy dont see a point to not just add buyable chest for the same price as a key.
Also, it would be nice, if you didnt have to buy 10 BE for 1 Event token for every token you have leftover. Its definatly not hard for it to calculate that you can buy more of it than once, cuz you can already stack key creation and capsule openings.