The reason is largely for safety for drivers who are less skilled in handling the car. In plain language, on many cars, including Tesla, the camber is set for more predictable handling in turns, which means more negative camber (the wheel tilted at the top toward the center of the car). This causes excessive wear on the inner tread of the tire. With less negative camber (recommended Tesla stock is -1.83 but a better setting for tire wear is -1.0) the handling in turns is somewhat less manageable for a less skilled driver, thus Tesla and other auto makers play it safe and set higher negative camber.
As mentioned above, it's the toe that really eats the tires. Much more than the camber.