Quote Originally Posted by Furious Mental
"I guess I just don't see the motivation behind this change."

Probably to make sure governors actually stay in the places they are supposed to be governing.
For what purpose? This wasn't necessarily historically true, and it's certainly not great for gameplay. If the Duke of York's troops were going to battle under the King, the Duke had jolly well be there.

Look at the bit in Henry V (okay, not the most historical document, but still) where they read off the names of the French nobles who were killed or captured at Agincourt. It's a long list of nobles who were present. Sitting at home (while maybe a good idea, if you were French around Agincourt) wasn't the norm.