Why is a firewall a good place to implement a VPN? Why not implement it at the actual server(s) being accessed?

What will be an ideal response?

Typically,
the
firewall
is
positioned
at
the
perimeter
of
the
protected
zone
of
an
organization,
such
as
a
company's
office
or
a
particular
network
segment.
Therefore,
the
firewall
is
an
entry
gate
into
a
domain
that
is
protected
(usually
both
physically
and
logically).
Encryption
protection
is
not
as
necessary
within
the
domain.
The
firewall
represents
a
single
entry
point,
and
so
it
is
efficient
to
install
a
cryptographic
process
(or
processor)
at
that
one
point
instead
of
having
to
install
one
at
each
internal
server.