"Humans are the versatile race once again. Just as readily as they mix with each other, humans mingle with members of other races. They get along with almost everyone, though they might not be close to many. Humans serve as ambassadors, diplomats, magistrates, merchants, and functionaries of all kinds (D&D 5th Ed)."
Humans are perhaps the most common race on Iyvis, owning large amounts of land on every continent and usually being welcome in places that belong to the other more common races. While they have almost the most amount of land, a huge amount of this is made up of small villages and the like, often poor with people struggling just to get by.
Contrasting this, some of their large cities are the biggest trading centres on all of the continents. While these places do tend to be filled with races of all kinds, humans are the owners of these and reap the benefits of them.
Most races are willing to mix with humans, a major more common exception being Tieflings, with whom humans have a large amount of hatred for, often keeping them as slaves.