It doesn’t hurt that putting a sealant kit and an air compressor in the trunk instead of a whole tire is cheaper for car manufacturers in addition to helping with gas mileage. Our colleagues note that most companies are skipping the spare now, in both high-end vehicles with run-flat tires and regular cars for regular people.
The argument against spares goes like this: most people don’t carry jacks or know how to change a tire, and will simply call a roadside assistance service anyway. That’s fine, but the problem is that certain kinds of punctures can’t just be patched and re-inflated. If you get a more serious puncture if some jerk actually slices your tire, or if you puncture the side wall by driving into a curb like I have totally not done three times, the car will have to be towed and the tire replaced or patched by a pro.