Blue Essence for Level 6 Champion Mastery?

This post is simply to share an opinion as well as to see what other people think about this issue. I am sincerely glad about the addition of level 6 and 7 champion mastery, however, was it necessary to make it a requirement to use blue essence? Since when was buying or earning chests and keys at all related to your skill level on a champion? I am frustrated because I received my 2 mastery level 6 tokens on Kalista, only to find that even disenchanting my 1 champion shard, I still sat at 458 blue essence. Using leftover RP, I bought 3 keys to open my 3 remaining chests, and all 3 contained 1 skin shard each, nothing else that i could use to get blue essence. As such, if I want to get my level 6 mastery, it will become less about my skill level on Kalista, and more about how long I wait for more key fragments and chests or how much money I choose to spend.

In conclusion, what was the necessity of requiring blue essence for mastery achievements? Am I alone in thinking this? And if Riot continues this policy, will there be ANY way to get blue essence other than opening a chest and hoping for the best?