Why do people think the crafting key drop rate is unfair?

I've read a lot of post about people thinking it's hard and unfair how the key drop rates work. I can easily get a whole key in a day or so of good playing. While you can only get a chest once a week. By that logic I can get a 4-6 keys a week playing hard where as only 1 chest.

Do you guys think the reward system is unbalanced? Also, why do people seem to have such a difficult time obtaining keys?