ESRB doesn't consider loot crates as gambling
TL;DR: It's loot crates are no worse than Pokemon cards.
Microtransactions have been a growing topic in the gaming world. They pretty much can be found in every game and will be featured in a majority of upcoming releases. This month alone, there have been stories of concern of Star Wars: Battlefront 2 microtransactions, the hullabaloo around Shadow fo War's DLC, the reveal of Assassin's Creed Origins' loot boxes, a leak for Call of Duty: WWII loot crates and the announcement of WWE 2K18's loot crates (but at least those have been confirmed not to require real-world money).
Loot boxes present themselves as mystery filled item boxes. A player typically has the choice to earn them in-game or purchase them with real-world money, but there's a catch - you don't know what is in the loot box until you open it.
Some folks have likened loot boxes to gambling. The idea is that without knowing the probability of in-game drops or knowing what we are buying, we are taking a chance, and that chance can cost us quite a bit of money.
While the pressure for developers to steer clear of loot boxes/loot crates is mounting, the ESRB is saying that these chance items are not considered gambling.
“ESRB does not consider loot boxes to be gambling,” wrote an ESRB spokesperson in an e-mail to Kotaku. “While there’s an element of chance in these mechanics, the player is always guaranteed to receive in-game content (even if the player, unfortunately, receives something they don’t want). We think of it as a similar principle to collectible card games: Sometimes you’ll open a pack and get a brand new holographic card you’ve had your eye on for a while. But other times you’ll end up with a pack of cards you already have.”
Basically, the loophole that the ESRB is using is that players have the option to use earned in-game currency instead of real-world currency and that just makes it 'simulated gambling.' This allows game developers to continue adding loot crates in games without getting slapped with a 'real gambling' sticker and getting set as an 'Adults Only' game (which would effectively kill the game's sales).
In addition to that, the ESRB noted that they note which games contain 'digital purchases.'