Ibn Umar r.a.huma related that I was with anNabi s.a.w., he s.a.w. prayed in safar (the travel/journey) not more than 2 rak'aat. And Abu Bakr, Umar and Uthman r.a.hum did the same. There are more ahadith on qasr, but I wonder if the 2 nas not enough ? or maybe Hanafi uses different nas... wallaahu a'lam