Some of them do have vents in the lid, which works for personal carry-home in your car. But for delivery, the driver usually has 3 or 4 pies at a minimum, in an insulated bag, so nowhere for the steam to go.
The obvious solution is a pizza oven on a vehicle chassis, where the pie is cooked en-route and delivered to you literally as it comes out of the oven.
Zume (died) tried that and Wonder (fleet of 500 vehicles) just ~failed ("Layoffs. Phasing out trucks. Searching for cost-efficient operating model."). Stellar Pizza (2-3 vehicles or so) is apparently still trying, their capex seems to be around ~$250K/unit.
The dominos box has had vents in the box for decades, and the heat bags are both heated internally by an inductively recharged element, and not sealed so that steam can easily escape.
The obvious solution is a pizza oven on a vehicle chassis, where the pie is cooked en-route and delivered to you literally as it comes out of the oven.