Also, it is possible the union sees no end-game in sight and is just trying to preserve jobs as long as possible. (The robots won't have a union, and if they did, this union would be unlikely to be a part of forming it.)
I think I agree that the UPS union's decision is possibly a poor one, but come on -- it's easy to see why they made it. Making self-interested, short-sighted decisions is literally what humans are best at.
(Plus, it's not like we can pretend to predict the future and better than they can!)
Arm chair "logistics experts" should go sling packages for a few weeks to see what it takes to compete with real operations before declaring existing operations dead if they don't "disrupt themselves". UPS, Fedex, and USPS aren't going anywhere.
My guess is that they overutilize seasonal/temp people and understaff later in the year from the unions pov.