I don't see why cam out should be ever desirable. Use torque wrench if necessary. Meanwhile, with Philips this turns out: screw is fastened with cam out torque ... some time later ... due to dirt, rust, etc. it now requires slightly more torque to unfasten, but that is higher than cam out! So now you have to wrestle to push driver stronger, each failed attempt wears screw more, and of course you can hurt yourself when it cams out when pushing strongly.

I agree that cam out is not usually desirable, however it could be used as a safety mechanism against excessive torque for the material being screwed into (although it's probably not the best way to implement a safety measure).