Ruling of raising hands in Du'a before Taslim

Usually while making Du'a we raise hands. But right after Tashahud and Darood-e-Ibrahim in salah before we say "Assalamu Alaikum..." turning both sides (Taslim) 1. because even that is Du'a, why don't we raise our hands? 2. If some school of thought does it, which school of thought practice it?