Earlier quoted context omitted.
I never heard of a battery warranty that wasn't prorated over the life of the battery. You know, if it fails 1 month before the end of a 5 year warranty, you get a credit for 1/60 the replacement value, often redeemable only as a credit towards purchase of a new battery of the same brand from an authorized dealer. I am sure you have heard of prorated battery warranties and are familiar with them, aren't you? Granted…
Hadn't heard of prorated battery warranties, but yes, makes sense. This fixes intentional abuse. But I imagine with free brick replacement, people would more easily and frequently forget to keep the battery charged. Without the risk of $40K, brick rate would probably go up.
It wouldn't really be free; the car would be out of service for some time. And Tesla could charge some kind of nominal-but-not-insignificant service fee. I doubt that the bricking rate would be sensitive to the actual dollar cost: as Tesla points out, it isn't that easy to do. Just being careless isn't sufficient, there would have to be other circumstances like a long trip away from the car where the cost of repair wouldn't have any impact.