(1) As for ...e5, ...e5 leaves the d-pawn weak at d6 and gives up hope of getting a pair of pawns in the center.
(2) As for ...a6, I'm not sure of its purpose, although I know the Najdorf is considered a "sharp" line, probably because of that risky tempo loss, and I know that ...a6 is important in other openings such as in one variation of the Queen's Gambit, largely to keep White's pieces off the b5 square, and to prepare for ...b5, which is a standard part of Black's queenside attack in the Sicilian.
now im little curious why this move is necessary. why black didnt play e5 directly? anyone know