Cast on Shock/Freeze vs Ignite/Crit

I need some help GGG. Cast on Shock or Freeze do a flat energy gain per application of shock or freeze. Cast on Crit or Ignite have that, but also have a multiplier based on their damage to ailment thresholds.

What gives? I know you can strip ailments and re-apply them, but is this the way? Why would anyone choose that vs crit? I am ignoring ignite since once applied, it would have to be consumed or refreshed, and I have not a build to test with (for ignite).

If I can just get more energy out of CoC, why do anything else? Seems build limiting to me.