The physical boosters are different, because they are set in stone and they're just there, ready to be bought. The odds are set and won't change.
With lootboxes, you allow dynamic regulation, which can be abused. For example, a famous streamer is opening your lootboxes live? Give him better droprate so that he constantly opens "Epic" items, so that his followers think it's so easy and want to try it for themselves too. See a whale opening your lootboxes? Starve him when it comes to loot for a bit to make sure he buys more lootboxes.
Another aspect is that the physical items take up actual physical space. You have to store them somewhere, and you have to look at them, and you might easier come to the realization that what you are doing is completely ridiculous.
And for the sellers of these physical items they also take up space, shelf space, and seeing a large number of extremely similar items for similar games in one retail location, might also clue you in faster on how ridiculous the thing is.
The physical items quickly run into physical limitations, which is good. The virtual items on the other hand have zero limitations, zero rules, it's all just pixels and database entries, and the presentation of what you "have" can be managed, hidden, manipulated, so that you still think you have nothing and need to buy more pixels.
Scratch-off lottery cards also are set in stone and they're just there, ready to be bought. The odds are known to the public (and probably right there on the card), the card has a fixed value but until you've bought it you just don't know if this card will be worth $0.25 or $500.
That's 100% gambling. And the concept is soooo very similar to booster packs.
With lootboxes, you allow dynamic regulation, which can be abused. For example, a famous streamer is opening your lootboxes live? Give him better droprate so that he constantly opens "Epic" items, so that his followers think it's so easy and want to try it for themselves too. See a whale opening your lootboxes? Starve him when it comes to loot for a bit to make sure he buys more lootboxes.