--prefix and include/library path

[Andrey Borzenkov]

So far all configure I have seen hard code /usr/local as base for
additional include/library path when doing checks (i.e.
-I/usr/local/include, -L/usr/local/lib, ...)

Is there any reason why autoconf does not automatically adds
$prefix/include, $prefix/lib etc (or more specific variants)? It is
logical to assume that if user has specified $prefix it also
contains other neccessary parts.

TIA

-andrey