lag compensating projectiles on the client decreases usability more often than you'd think.
Projectiles like rockets apply a lot of forces to the player which are not easily predictable. If you fire a rocket and client-side prediction has it leaving your vicinity without collision but the server has someone stepping into the path of the rocket so it explodes close enough that the explosion exerts force that changes your position, you're going to have a really bad misprediction on the player's position, which of course can get waaaay worse if the player launches another rocket while the first rocket's effect on player position has not been sorted out properly.
Projectiles like rockets apply a lot of forces to the player which are not easily predictable. If you fire a rocket and client-side prediction has it leaving your vicinity without collision but the server has someone stepping into the path of the rocket so it explodes close enough that the explosion exerts force that changes your position, you're going to have a really bad misprediction on the player's position, which of course can get waaaay worse if the player launches another rocket while the first rocket's effect on player position has not been sorted out properly.