In a titration between oxalic acid (ethanedioic acid) and potium manganate (VII), why would you need H+?

You can add sulphuric acid to provide H+ protons for the reaction, (we didn't- we heated the solution of oxalic acid and iron solution together to about 60 degrees) but I want to know why you would add it if you were going to- what effect would it have upon the system?