If the minor has a city then the major will conquer it and absorb the new zone - no problem. However if the minor does NOT have a city then the major does not really know what to do. The minor will not be conquered and might even stay there the length of the whole game!
This means minors without cities can be used as an effective buffer zone against a major indefinitely (ie cheese strategy). This is the reason that some majors snowball and conquer the whole map, but others stay small - because they were boxed in by one of these minors.
Requested change: Majors should wipe out these minors as well
