More often, in the particular cases I'm familiar with, we're talking about commercially sensitive information, where we have to weigh up the costs of complete end-to-end encryption by default against the loss of productivity that results when things like big network file transfers slow way down. In a self-funded small company, with limited staff time and limited cash, total encryption is not always the answer.

For example, I think you can reasonably have a policy that encryption of any removable media is required but anything screwed into a rack in the office is biased toward performance, and in fact that is basically what we do in most cases. But it does limit the value of the kinds of warranties we're talking about, because we're not going to just hand over a hard drive that has probably had sensitive company documents on it to some random delivery service.

Similarly, from a personal point of view, I don't consider theft of my home computers to be a very high risk, so I don't routinely encrypt all the hard drives, even though I have some potentially sensitive data like downloaded bank statements and bills on there. Instead, I expect to keep the hard drives for a relatively long time anyway, and then have them securely wiped/destroyed when they are too old/broken to be useful any more.

Just to be clear, I'm not saying these choices are anyone's problem but my own. I accept the cost of the occasional hard drive failure as a natural consequence of these policies. I'm just saying that it means hard drive manufacturers' long-term warrantes are effectively not worth anything to me or the companies I run. I suspect that in practice plenty of other people/small businesses follow similar procedures, and therefore the warranties probably aren't worth much to them either.