Gregory XI (Pierre Roger de Beaufort) was the last. Does it all come down to the Avignon papacy, which ended two years earlier? Is Rome wary of French Catholics, even after almost 650 years?
Since 1378 only a handful of popes were not Italian. Namely Callixtus III and Alexander VI (both Spanish), Adrian VI (Dutch/German), John Paul II (Polish), Benedict XVI (German) and currently Francis (Argentine). The first three between 1378 and 1522 and the last three between 1978 and now. Just to put your question into perspective.
Hey there,
Just to let you know, your question is fine, and we're letting it stand. However, you should be aware that questions framed as 'Why didn't X do Y' relatively often don't get an answer that meets our standards (in our experience as moderators). There are a few reasons for this. Firstly, it often can be difficult to prove the counterfactual: historians know much more about what happened than what might have happened. Secondly, 'why didn't X do Y' questions are sometimes phrased in an ahistorical way. It's worth remembering that people in the past couldn't see into the future, and they generally didn't have all the information we now have about their situations; things that look obvious now didn't necessarily look that way at the time.
If you end up not getting a response after a day or two, consider asking a new question focusing instead on why what happened did happen (rather than why what didn't happen didn't happen) - this kind of question is more likely to get a response in our experience. Hope this helps!