The short answer, ignoring everything but differences between cars I think is at least a portion of this:
Different cars have different aero, lets say a Red Bull with a lot of downforce and a McLaren with less downforce.
Now think of 130R at suzuka, high speed corner. The RB can probably pull more Gs here and so it will roll more and the "ideal" amount of camber is different than the lesser high speed cornering McLaren.
This is super simplified but I think may be what you are looking for.
That is an explanation for one corner, on one circuit between two cars. Obviously as you begin to consider all the corners, tire wear, driver preference, difference between car suspension, aero, roll rates, caster, chassis stiffness so on and so forth it is not at all unreasonable to see different teams(and even same team but different drivers) running different camber rates.