Dual Role - Is it simply Double pay check game?

To my memory, I hv not seen more successful movies with the heroes in dual role.

Eventhough there were commercial hits with dual roles, movies with interesting story plots are very rare. You can number it easily for any heroes..I am listing down some of the last movies in which these guys performed in a dual role.. italics are supposed to be the hits with proper story content. Others may be commerical hits, which didn't impress that much.

Rajini (Raajathi Raja, Muthu)
Kamal (Apoorva Sagothararkal, MMKRajan, Indian)
Vijaykanth (Vaanathai Pola, Thavasi)
Satyaraj (Looti)
Sarathkumar (Naatammai, Natpukkaga, Ayyaa)
Arjun (Karna, few more after this.. which are not greats)
Vijay (Puthiya Geethai)
Ajith (Vaali, Villain, Attagasam)
Simbu (Manmadhan)

Very rarely, strong stories have come out from the above lot, eventhough others may be commercial hits.

The reason behind sharing the above info, is my curiousity as to why these guys are signing movies again & again in dual roles? Are they getting double pay checks? Why do they want to fail again?

Take the upcoming movies -- Vijay's Sivakasi, Ajith's Godfather, Simbu's A-C. It is a pure gambling by the producers. Actors don't bother, isn't it??

Still a question lingering in my mind? Is Vikram Playing a dual role in 'Anniyan' or not (Initial talks were like that)? If so, I hope Shankar makes it differently, as he did in 'Indian'.