How is a shock sensor any different? Even if it's on the outside of the box, the pickup guy isn't exactly trained to confirm it's in good shape, he's not signing anything to certify that the sensor is intact and operating properly.
And as far as I know, none of the major carriers actually declare anything like "packages will not be subjected to more than X G-forces during transit." So even if the sensors did trip, that only indicates that they tripped. It doesn't prove the shipping company did anything 'wrong'.
And seeing as the guy behind the counter or on the phone isn't an expert in accelerometers, any explanation is going to be over their head. And once again, how do you establish you didn't mess with the accelerometers ahead of time?
I can actually understand the human-nature behind trashing something marked fragile, or something with shock sensors stuck all over the exterior. Not that it's justifiable. Basically, you're saying that this person treats all the normal packages like shit and just throws them around for no reason. That they're not even trying to be good at their job by default. Not to mention that you're asking for special treatment without providing additional compensation.
Which explains the best way to keep your package safe. Insure it. You probably don't even need to insure it for the full value. Just spend the 70 cents to get $200 dollars coverage. Everyone handling it knows there will be an internal follow up if the company has to pay out on the claim, because it actually costs them something.