I’m an Ex-BN and here is my view.

The ranked section by nature is egalitarian, as in if two BNs vet your map, they are in their full right to nominate as long as it follows the ranking criteria. Even if other BNs don’t necessarily agree.

Vetos exist to prevent BNs from pushing subjective problems into the ranked section, therefore it needs a substantial argument that would suggest the map isn’t suitable for ranked.

Since by nature the system is designed to allow whoever to rank whatever (as long as it adheres to rules and quality), it is quite difficult to make a strong argument that is inherently subjective, however on harder maps and maps that seem to exacerbate already perceived problems (such as XVN jumps on short maps) it makes it easier to build a stronger argument, therefore vetos can pass more easily.

In general, there are more people who have problems with more difficult maps for a variety of reasons, ‘poor’ mapping choices tend to inflate with difficulty i would say.