The enemies do cast them, but they probably get hurt before the charge is done.
Whatever battler is attacked, it'll lose its charge.
To get rid of it...
Open up your script editor, press ctrl + shift + f, and search "@charge = nil"
They'll be 3 instances of them. Comment them out, and now battlers won't lose their charge.
Edit:
It seems to me... that there might be a slight bug with the knockback.
When I hit an enemy for the first time, he gets knocked back once.
Then the second time (using same attack)... he gets knocked back even more... and even more on the 3rd, 4th, 5th, etc. hits.
Then if the enemy does an action (it hits me), the knockback resets back to once and repeats the pattern.