Reason don't come into it, YaRRR! 
Back in the beginning, animation times weren't factored into balancing powers. Fire got lucky with just over 1 second. Most Controller holds weigh in around 1.6 to 1.8 seconds. Tesla cage in Electrical Blast has always had an animation of 2.1 seconds, and I guess that's just been copied across to Electrical Control.
The Blast sets used to be more like this, and had all Tier 1 and 2 animations normalised to 1s and 1.67s a few issues back. Maybe the same will happen to Controller ST immobilises and ST holds one day? Possibly when the alternate animation system gets spread out to Controller sets?
Until then, its just the way it is.
Ahhh....I found the activation time of single target hold of Electricity Control is the longest, almost doubling Fire Control. I am not sure the reason but, I think why Fire Control can has that fast activation time, but Electricity Control cannot?