If you wish to Buy Region, you can't if:
- you are already a lord
- it has a lord
- you are within the capitol perimeter
- your amount of family gold
- perhaps other things
But,
If you are a Lord, it says you need to step down first, without telling you that there are all these other issues why you still won't be able to buy it, causing players to step down & have to be re-appointed. I think in this type of situation, all the obstacles should be listed. This is more a case of a bunch of nested "if" clauses than any intentional design, as far as I'm aware.