Why Heroes interfere into directors work

Gen X star Jr NTR has reportedly cancelled the shooting of his ongoing film Rabhasa (Working title), causing huge loss to its producer. Apparently, a song was scheduled to film on NTR and Samantha for 5-long-days. But Tarak's differences with director seems to have cost bomb to producer. With this, producer Bellamkonda Srinivas reportedly incurred more than Rs 35 Lakh. Apart from loss of Rs 35-odd lakh including the cost of a specially-erected set, producer now has to re-arrange the dates of busy bee Samantha and choreographer and team, later on.  

A confidential source in the unit confided, "Even though, director Srinivas briefed and convinced NTR about the concept and reason for the song in the screenplay, but NTR had second thoughts and allegedly cancelled the shooting and asked director to re-work on the song."

Earlier, the Nandamuri scion also forced cancellation of the shooting of a portion in Ramayya Vastavayya since he accidentally, shaved off his mustache, so producer Dil Raju has to re-arrange the whole episode after few months. 

This does not happened with NTr only but also few other heroes who interfere into director's work. recentely we have seen that Pawan Kalyan is not satisfied with sampath Nandi. Why do these heroes have these habbits.

Cannot T-Town change on these aspects.