The Isle of Armor is essentially a training ground. Everyone there is focused on their training, and it's very unlikely they'd waste time by standing hours on end, waiting for potential opponents.
The Crown Tundra seems very research-based, as seen with the Dynamax Adventures and the expeditions performed. The people there are probably very focused, and can't waste time. The people in Freezington don't exactly look like tough Trainers, and many people would probably rather stay out of the cold instead of waiting for other opponents.
Hope I helped!