In SP, most of the villains last for about 3-5 months (except Kaveri - she is perpetual). They do all the nasty stuff in these months. The audience gets emotionally attached to the plot. However, when they are exposed, they are exposed in a couple of episodes and that too they are excused for their behavior or given to police (We all know how great our legal system is !!). So where is the satisfaction of the audience? The mental, economical (TV, cable power) and time that the audience sacrifices goes in vain.
Atleast in movies, the hero actually beats up the villain (counting this is for my mother, this is for my sister etc) giving much satisfaction to the audience. This is why AB was successful as an angry young man and the reason why the ending in Sholay was changed (Yes Sanjeev Kumar kills Gabbar, I have seen both versions) instead of Gabbar going to the police.