I have not played the game, so this is only from what I've read [0], but it is my understanding that they designed a progression system that strongly pushes people to pay. Also, while not strictly "loot boxes", you are still able to indirectly pay for random items because the drops are linked to level progression, which can be sped up with micro-transactions.
[0] https://kotaku.com/the-free-gear-in-black-ops-4-is-an-unforg...