That, and they purposely match people who buy lootboxes, etc to people who don't so that those people, being at a disadvantage, loose and are then pressurised to buy them.
I don't believe Epic or Blizzard have any games with non cosmetic items in loot boxes. Perhaps they "purposely match players with cool skins with those who don't" to make them want to buy them though.
Hearthstone packs definitely affect gameplay. Most of their other games are cosmetic-only, though.