Face it. Some people cannot buy CE, restricting 3-5* crafting and guild making. So that's why we should be "rewarded" for certain achievements.

Example: if you kill 1,000 enemies, you get 100 CE.

We could also be rewarded with Crowns and Mist Energy tanks.

There would also be a "continuous" reward.
Example: you get 100 CE for every 5,000 enemys you kill

PROs

Crafting
more Guilds
satisfied players
more reasons to play

CONs

Free CE (con for the company)