ON the map
While it is a fun little thought I doubt that the planners of the US highway system put much thought into those numbers crossing. I can tell you that north-south numbered highways are numbered lowest west and highest north and end in an odd number. Then the east west highways are numbered lowest south to highest north and end in an even number.
"But Jason, I69 runs east out of Lansing!" I hear you. What does it do as soon as it leaves Lansing? It dives south and quite a bit west until it hits a little after Memphis and turns into some local highways and not quite making it to the Gulf of Mexico.
Triple digit numbers tend to represent by passes or circle major urban hubs like big cities.
So to answer your question it really is just a fluke of how we drew our maps and laid down our roads.