The haggling involved in car buying is a choice. Over the years various sellers have used “no haggling” as a selling point, Saturn for instance. But I can walk into any dealership and choose to pay the listed price without haggling.
Assuming you pay via dealership financing that is likely true but many dealerships have a different price for a car if you are paying cash for it.
They have multiple avenues for haggling beyond price. Leveraging loan terms or penalizing you for cash, insisting on addons like 'safer' blinking tail lights that they auto-install on every car, the creativity never ends.