Despite feeling that all the wagon/cart changes are against me personally I'll go ahead and ask.
Quote- Need one hand free to pilot things now, unless your skill is at high advanced
You stop skilling up on a cart the very moment you hit advanced period from my experience.
(No more fails)
I think, like the Ride skill, it caps out at a certain level for characters that don't have it in their skill list.
The PC in question caps out at master.
I feel like it's more to stop solo skimming trips, because if you can't do combat while floating around, you're gonna be at a huge disadvantage.