Why does the Ghazal stand as the most popular of all classical Indian musical forms despite not being considered by most singers?

There are a couple of issues raised in the question.  On
one hand, I think that the ghazal's lasting popularity represents how the power of
tradition is still a part of Indian identity. The ghazal's history stretches back
generations.  At a time when Indian cosmopolitanism as well as India's active
participation in a globalized world might do damage to some aspects of its traditional
culture, the ghazal stands as an element that thrives despite its age.  From an artistic
point of view, the ghazal represents the very essence of classical training of the
singer's voice.  Part of the reason why few singers are able to embrace the form is
because the ghazal requires a classical sensibility that demands the highest of
training.  Only the most talented of singers could attempt to sing the ghazal.  Artists
like Mohammed Rafi, Hariharan, and Pankaj Udas are few of the crossover artists who
could sing popular music while adhering to the strict standards of the ghazal.  Nusrat
Fateh Ali Khan and, more recently, Rahat Ali Khan are also examples of the artists who
could span both domains.