Comment by imtringued

It sounds like you haven't played War Thunder. The service manual is obviously useless in War Thunder because repairs happen automatically under a cool down. The point of the game isn't to learn how to operate any specific vehicle. The point is to act as the commander with high level controls but with some skill based elements such as aiming.

Meanwhile the technical specs of the tank.... Those are absolutely critical because the damage simulation is entirely dependent upon them, because this isn't world of tanks where tanks have hitpoints. When you shoot a projectile, the projectile interacts with the armor, creates spalling (or explodes inside) that then has to kill all the personnel inside the vehicle for it to count as a vehicle kill. Shots that don't kill can disable parts of the tank, activate the ammo rack, destroy the tracks, etc.

A service manual isn't going to tell you how thick a specific section of the armor is, or what composition the armor has or what angle the armor is. Yes this still retains a sort of arcade simulation feel, because a realistic simulation such as this [0] is computationally too expensive to happen in a multiplayer game.

[0] https://www.youtube.com/watch?v=eASJbjtw180