This definitely isn't a universal experience and there are definitely a lot of trading card horror stories, but for me + friends growing up the purchase of trading cards had a different place in life. They were like one of life's small rewards you had a chance of rolling whenever going into a shop with a parent/guardian. Being at the checkout, putting on the little kid puppy-dog 'pleaseeeeeee' and the adult deciding if you've been 'good enough' and possibly giving you something for that. Acquisition was separate from their consumption and social role.
With lootboxes, you're actively pursuing the purchase to immediately try to meet a goal. You want the purchase, make it, have the question answered of whether your roll was good or not and that's mostly it. Trading cards were taken home (or at least to the car), physically admired, stored, socially shared even if they weren't 'worth' sharing, and had a larger variance in subjective value for trading or gifting later.
With lootboxes, you're actively pursuing the purchase to immediately try to meet a goal. You want the purchase, make it, have the question answered of whether your roll was good or not and that's mostly it. Trading cards were taken home (or at least to the car), physically admired, stored, socially shared even if they weren't 'worth' sharing, and had a larger variance in subjective value for trading or gifting later.