Just a guess question. But how big do you think regions are?
Outside of flying a plane, or riding in a car, Ash and his friends usually travel on foot.
But it would take me a day to travel on foot about 30 miles (assuming I didn't die trying in the process).
Now I realize it can't be as small as in the games (technical limits), but is traveling on foot through a region faster than traveling through a state or country on foot?
Or is it possible there are other modes of transportation that are being used (off-screen), to explain a lot of what we see in the anime?
So I'm not sure.