The Most Fundamental Principle.
The overarching principle that drives almost all other design considerations was simple. It has to be cheap. The full benefits of RV-C comes when the network extends to every nook and cranny of the RV, including low-cost items such as water heaters and light switches. RV-C is not intended just for high-end motorhomes, but for RV's of all types and prices.
This principle drove the initial decision to work with CAN as the base protocol. Almost all microprocessor suppliers include products with built-in CAN controllers, making CAN the cheapest protocol to implement at the hardware level. The net additional cost of implementing RV-C in a microprocessor-controlled product can be as little as a dollar.
Cost was also the driving factor in another key decision. Whereas many other CAN protocols require shielding, the RV-C committee was skeptical of the benefits of shielding in light of the costs. Shielding requires more expensive cable, and connectors have to be attached by hand in most cases. Thus it drives up the cost of wiring considerably. The committee was reluctant to require this expensive step.
The debate included both theoretical considerations and lab testing. The conclusions obtained were that while shielding theoretically can reduce interference, in practice it usually has little or no benefit. And in some situations it can actually create or exacerbate problems. The committee unanimously agreed that shielding would not be required by the protocol. RV-C does not prohibit the use of shielded cable, but it is neither required nor recommended.
Not surprisingly, the trend among other industry groups has been in this same direction.