What is the need for shell when executing tclsh

What is the need for shell when executing tclsh

#!/bin/sh
# A Tcl comment, whose contents don't matter \
exec tclsh "$0" "$@"
why should we invoke shell here (#!/bin/sh) .
We can directly invoke the tclsh (#!/bin/tclsh) .
Why we are First calling the shell and again inside the shell we are
calling tclsh interpreter .
why people prefer to use these (#!/bin/sh , exec tclsh "$0" "$@") . Can't
we execute tclsh direclty ?