I do not ascribe any sinister motive to that...The opportunities for TB's are vast in this globalized world....
In the 30's & 40's the cine actors also had the onerous task of singing...So we needed a different breed...
I chanced at the following article...Even in 30's you had the famous cine artists -M.K.Thyagaraja Bhagavathar, T.P. Rajalaxmi, K.B.Sundarambal from other communities who were successful...So charisma plays the key role...Who would not get swayed by the Bhakthi in KBS or MKT songs
1916-1936
In the 50's to 70's period Government jobs were the ultimate for TB for a comfortable life...The high paying jobs were in arts (cinema,drama, music in that order) followed by Medicine/Engg/Legal...The cineworld had a few producers who were willing to invest a few crores, nay few lacs for producing a movie..Artists were well paid & being an actor was a coveted job.
As far as cine technicians are concerned, there has been a steady increase in education level & skill level of other communities too (which is welcome) and hence TB's are no more the only torch bearers of that
From the late 80's the private sector has grown in leaps & bounds...In this globalized world the private sector is coveted for its high paying jobs...While the cinema has just about a dozen highly paid artists in the private sector it runs in to thousands..No wonder the charm of cinema is eroding and our TB's run behind the private sector
While there has been social justice themes in Tamil Cinema starting with Parasakthi, the TB's are not stigmatized in the arts field...They are always welcome to add to the charm and color in the cineworld...