Vedic Sanskrit and PIE

On another list, a question was raised if namaaz (Arabic) is somehow
related to namas (Sanskrit, PIE?)

How essential is knowledge of Vedic Sanskrit for PIE studies?

If Vedic Sanskrit is very distant from PIE because of adstratum,
substratum influences of languages such as Munda, Dravidian, and even
the so-called Pra_kr.ts (however, loosely defined) isn't it more
appropriate first to isolate such influences to arrive at the core
PIE in Vedic Sanskrit?

It appears that study of PIE is not essential to study Sanskrit
linguistics. Sanskrit may have to be evaluated in reference to the
languages of India. PIE studies may help evaluate the extent to which
Sanskrit is related to IE languages. If so, why should Sanskrit
scholars be asked to study PIE linguistics?