There is certainly a follow the leader mentality in video games. If there's a new successful game design formula or way to monetise you can be pretty sure it will be adopted wholesale. While loot boxes as a concept, the idea of spending a currency (in-game or otherwise) to purchase random bits of content, is something that's generally accepted in free-to-play games or in sectioned off modes (like FIFA's FUT), in traditional AAA experiences it is typically frowned upon. The general notion is that if you pay full price you don't want to have to buy anything more to enjoy the content.
Microtransactions are a red flag to many gamers. Recent examples like NBA 2K18, Forza Motorsport 7, Middle-earth: Shadow of War and the upcoming releases Assassin's Creed Origins and Star Wars Battlefront II illustrate that not only is this now a widespread phenomenon (when it comes to both publishers and genres) there are also various issues you can take with it.
The criticism can fall into different categories. In the case of NBA 2K18 you're not unlocking loot boxes per say, but you're upgrading your character and buying customisation items, and the benefit of buying that currency is massive and lets you skip hours and hours of grinding. Forza Motorsport 7 offers prize crates as a means to unlock its content. While you earn credits in both these games, clearly you'll unlock things faster if you just spend some real money. One of the key components of loot box design is to make it so that the player isn't in control of what they're unlocking next. In some cases it goes completely against objective-based game design. Player agency is sacrificed in order to promote an additional revenue stream.
Let's be honest. Loot boxes as such isn't great game design. It's a raffle mechanic that is about as inventive as a slot machine. Start players out with some free coins and watch them pull the lever. It's not without reason that the games industry and the online casino industry has close ties, but is it really the route this industry wants to take? Offer free drinks as the punter steps in, and they sit down for a long time, pulling on that lever (apparently it's just button-pressing at casinos these days, but you get the point).
Whether it's FIFA Ultimate Team or physical trading cards it encourages a gambling mentality in young kids and potentially makes them spend more than they can actually afford. Afterall, if grown-up reasonable people like TotalBiscuit (the popular YouTuber's take on loot boxes and gambling can be seen here) can fall victim to these methods, clearly young children are at a much greater risk. Sure there are ways to safeguard against this for parents, but there is certainly a seed planted there in children, a seed to lets them know that if only they'd spend some more money they'd be more successful in the game.
Over in Asia, the "gatcha" design philosophy, which FUT certainly falls into, has become dominant and it has clearly stifled creativity. If you wonder what turned Konami away from big blockbuster AAA titles, it's this. This is something that as gamers we must stand against because this is a very real threat to the entertainment form we've come to love.
It is pretty clear that the industry is going to be reluctant to self-regulate these practices. ESRB was recently approached about sign-posting loot boxes as gambling, but they felt it didn't fall under that definition. Companies are obliged to maximise revenue, it's the way publicly traded companies work, but in the longterm, this sort of practice could lead to serious issues.