Simple, because Enlisted is nowhere near as popular as War Thunder and is dying, at least from what I hear, and, as I’ve stated before, is basically a mode of War Thunder that was arbitrarily spun off into its own game. The only things that made it ‘not WT’ was in the ‘backend’, how you acquire your units and so on. Since then, however, the game has become more and more like WT, with progression and matchmaking becoming in line with how WT does it, only with fleshy humans.
It would also greatly expand the content that can be implemented into the game. As it stands, WT is nipping at the heels of the big content that can be added. They aren’t out of it, to be clear, but if they continue pushing forward they are going to run into the issue of either having to wait for new vehicles to come out IRL, or have to start making things up from scratch, which would go against WT’s identity. I get the argument that they basically do that right now with how new the vehicles are, but there is a difference between making up stats for a classified vehicle and completely fabricating a fictional vehicle. Even going wide isn’t much of an option. While there are nations that can be added, none of them come without issues, and will run out eventually, even if they rework tech trees to allow for multiple sub trees.
They expand to infantry, however, that gives them a whole new avenue of content they can add, such as dedicated engineering vehicles, APCs, transport aircraft, light unarmed vehicles, and so on, as well as greatly expanding the amount of nations that can be implemented, with infantry being the justification. Would also have the added benefit of allowing them to revisit tiers and give vehicles hype, as now people would have to consider what is viable for top tier infantry.
It would also increase War Thunder’s market, as now FPS players would have an interest in the game, which, in turn, would increase the game’s reach. There’s a reason why War Thunder is, like, 3 to 4 games in one, and Gaijin didn’t split off its titles.
Honestly, in retrospect, it’s kinda weird they did Enlisted at all, and didn’t just implement as a mode in War Thunder. They didn’t for ground, they didn’t for naval, and seeing as how Enlisted has become more like WT over time (in terms of ‘backend’ stuff), any reason for a split has kinda just dissipated.