Because the whole point of a plague is that it's something you can't prevent, it affects everyone, and it's devastating. If you change any of that it's not really a plague anymore.
First I've ever heard that definiton of plagues. It's usually used in the sense of an infectious disease that's particularly calamitous and wide-spread. I'll talk of any typically medieval disease from now on - poxes, dysentery, consumption etc.
And the problem with this is that it's antithetical to a game where you choose different strategies or react in interesting ways to stimuli. For the most part, plagues and most other natural disasters just slow down the game.
It can be a way the world reacts to you in that certain choices render an outbreak more probable, such as:
- High death counts, refugees, or war attrition in general..
-.. Poverty, also connected to maybe low sanitation
- Increased inter-continental (/-factional?) travels
- Not taking the time to bury the dead after battles
- Poisoning water supply
- Flinging disease victims inside towns
There are much more obviously, these are just a few that readily come to mind. As mentioned before of course we don't live in an ideal world meaning that in Bannerlord water doesn't matter, battles regardless of scale leave no trace behind the region, sanitation isn't a thing and so on and so forth. Point stands though that it is possible, and can have interesting consequences and results that make the world feel real, such as:
- Characters and the world reacting to your choices as a warlord in protesting brutal biological warfare, viewing you as less honourable for not adhering to rules of war and burying the departed, governors being spoken out against for not taking appropriate measures, or rulers for dragging out destructive wars - not to mention the civil unrest
- Settlements going into quarantine, restricting entry, reflected visually in town scenes
- Armies also suffer from the effects of disease and could increase desertion rates
- Something small but interesting is that forces that have brought pestilence in their earlier conquests could induce dread in the people in their wake (radius), just a thought
This feature doesn't give you complete control on disease inflicting your domains but I don't see why it should. There's no harm from my view in the world throwing unforeseen challenges your way if it serves to make the game more immersive and enjoyable.
Like off-map invasions and civil wars / rebellions, it's the third horseman in the "this sounds cool but actually sucks" strategy game apocalypse.
If implemented badly.
Holy moly, people are really out of touch with mount and blade if they think plagues would fit in mount and blade in general. I don't even know any mods in previous titles that has done it either because of technicality or it just doesn' fit in the game as mentioned before. I believe the only module to have this feature was WFAS and even there it was limited to army attrition when you're out of food. Hell it isn't even a plague.
Why are you getting sideways with me for we're just talking, you're not in danger. Oh but you didn't mention me by name so it's all fine I guess.