First of all, it's not usually Rome that grants a nullification of marriage. It's the Diocesan tribunal.
Secondly, if the tribunal refuses to declare a nullification, the only positive option for the petitioner is to appeal to Rome, not the tribunal that just turned him down. Why would the tribunal suddenly reverse itself?
Thirdly, it sounds like you are very pro-"annulment" and the less doors one has to knock on to commit adultery, the better.
I’m just saying it’s crazy for anything to have to go to Rome.