Sivachidambaram is basically unused because he is well off with his forte as a classical and devotional singer. His arena is different with Tamil scholars, Divinity centres and academic universities including the recent Tamil virtual university available at tamilvu.org. That apart he is a transplant doctor. He is not like other singers and he is unique with his talents AND self respect. M'sia vasudevan, SN Surendar, TL Maharajan, Deepan Chakravarthy and his brothers, and a loooooong list of wait listed tamil tongued singers.
Same reason apploes here.
Just being a MD doesnt give a liberty to risk with voice. He could have given songs like kudumban oru kadamban to sirkali but he sang himself. We dont have much mythological movies now. Even pathos songs are gone case now. Every thing is romantic crap or gana crap.