Add one variable to your example: imagine that having variations increases cost such as increased development cost (you need to develop each component, test and certify possible combinations, incur increased logistical complexity, etc..)
This additional cost however is less than just adding the higher trim to every configuration, e.g. the additional room, so it doesn't make economic sense to do so.
But let's assume you now get the ability to sell and unlock a higher trim after the initial purchase. Let's say that 20% of your customers would be willing to purchase such an unlock at a later point in time, resulting in increased revenue.
If that revenue plus the reduced lifecycle expense exceeds the cost of adding the higher trim as baseline you would have a business case, which wouldn't be the case if you just add the room for everybody (where you'd have to raise the base price and lose buyers on the lower end).
