Pot still Temp control - Why?

[pochine]

I have read so many posts about controlling the output rate of a still but no reason why.

I have a 50lt keg boiler and a 2400w heating element with no controller.

I have made 2 rum washes and the results were not what I expected. Most of the cuts smelled and tastes of tails.

Does the heater controller reduce smearing?