He helps the team every day as the DH.
He could field 1B, but we have other options over there. Why should Ortiz play 1B when we have the Greek God of Walks over there, manning the position very capably at that?
I'm not disputing Ortiz' ability as a hitter. I'm just saying a DH should never win the MVP. They have their own award and he positively deserves whatever that award is.