Motor placement (the "why?")

Brand new, first post here. I been looking for plans for a 3dof (pitch,roll,yaw) for mainly flight sims. Searching "plans", I've found many geared towards racing, heavily focused on pitch, roll, and heave. Not much for pitch,roll, and yaw (unless it's added later as traction loss). One thing I've certainly noticed is that nearly all 3dofs have both the pitch and roll motors either in the front, or both at the rear. Again, I'm new to this, but is there a particular reason for the pitch to not be in front, and the roll on the side? Thanks for any insight on this topic. Brian

if two motors are on the same side (front or rear), then to implement the pitch or role they act simultaneously (the load is divided between two)

if you put one in front (for pitching), the second on the side (for roll), then the motors needed are 2 times more powerful compared to the first solution

Great to know! At this point, I was under the impression that each motor controls it's own axis independently. Thank you.