I'd wager the largest volume of people staying at the poly/etc are not leaving WDW every day for meals, etc. Are people making grocery runs, etc.. yes. Are people visiting non-WDW... sure. But that kind of traffic isn't the ones leading to mass congestion... or the need to get people off the roads. Where I bet the number of people are using their cars is to avoid being on the buses/etc is far more.. and much more of an impact -- their travel patterns would be a lot more similar with other people on property, etc.
My point being is... simply putting the cash fees as 'just gravy' is disingenuous IMO. They could easily allow people to have cars for all the valid reasons people do and still constrain and even greatly reduce... their churn on property. They KNOW a large portion of their customer base as valid and unchanging reasons to have a car on property. They also know charging an extra $100-150 a trip is going to largely **** off their customer base.
So why would you put those things together unless the potential $$ outweighs the negative consequences and punishing LEGITIMATE customers who are doing exactly what you want... coming to WDW and staying all week and being loyal. When you said penalize 'everyone' - that's exactly who Disney is penalizing in this choice.
They could easily have moved to a exit pay system with validation options. A model that would allowed 'loyal' guests to have 1 exit for free.. so they never pay for a full length stay. You could add validation for people that actually buy a entree... you could have validation for those that ACTUALLY leave in under 3 hours. This is a proven model that is used WORLD over... Disney has to invent nothing.. and would have achieved the goal of discouraging in/out behavior and avoided penalizing ALL the use cases Disney wants to embrace.
Instead they goto a model that penalizes ALL resort guests... still gives F&B their free parking exception that is impossible to enforce reliably and cheaply.. and lines their pockets with guaranteed revenue week to week.
And we still argue $$ isn't the lead factor? I say baloney.
Remember.. you lead into this not arguing 'strengthing the captive lock on customers' - you said "Get people onto the busses and out from behind the wheel".
DME can do fine on its own for ensuring people are WDW-locked. Penalizing those who go the extra mile to have a car, or need a car.. disney is just giving them the finger.