was no a/c in hubs years ago, package handlers would occasionally pass out. I used to run a clipboard for audits, even that was oppressive in summer but you got through it.
drivers for decades did it without a/c. sure it’s nice but not necessary. I am sure those vehicles get crappy gas milage and with a/c and then opening and closing doors frequently = equals a lot of expense.
and climate change believers will complain about the added harm to environment. these teamsters are mostly dem voting anyway if they follow what their union leaders tell them. maybe they are going electric vehicle? even more expense.
a/c in the trucks is almost impossible. large metal cans, engines off at stops.. the system would never work.
they would have to use a system like semi sleepers have. It might actually be cheaper to install APU (auxiliary power units) than replace the fleet anyways.
APUs have small engines (gas or diesel) that run an a/c system, generator and heat coolant.
I worked for a utility company that uses the same basic vehicle as UPS. They had A/C. Constantly quit, only an outside contractor an hour away could fix it and it really was worthless. Truck was sweltering with A/C on in it. Just too big an area for one little system to handle. Plus absolutely no insulation in the cab area. I used to take them up for repair, and just left the doors open driving, that was tolerable...just make sure you wear your seat belt....