Plate armor is heavy… and relatively cumbersome. And while any good knight has trained to wear heavy plate armors for long periods during times of conflict and war (or pomp and ceremony), the idea of existing in plate armors day-in and day-out is an arduous thought.
Any character whose armor is of the following types:
…in our game, we choose to understand that, except chainmail, the character is wearing the equivalent of Chain Shirt armor underneath (Chainmail is a Chain Shirt with other stuff added on, but it functions the same for our purposes).
We will assume that the character lives their day-to-day life in the equivalent of Chain Shirt armor (traveling, resting, in a rough town), and only gets fully armored up when they anticipate combat or is expected to appear in armor. A fully armored fighting man on a fully decked out warhorse entering a rural town will cause fear and panic… It’s a sign of war. But a fighting man in a chain shirt, riding a wagon with a majestic warhorse in a halter following along would be cause for excitement and spectacle!
This will make more sense as we play the game.