> tradeoff between security and convenience they'd certainly have far fewer customers

What? Most people, thinking through the tradeoff, would 100% not choose to be in charge of safeguarding their own key, because they're more worried about losing everything on their PC, than they are about going to jail. Because most people aren't planning on doing crime. Yes, I know people can be wrongly accused and stuff, but overall most people aren't thinking of that as their main worry.

That's exactly what I mean.

If you tell people, "I'll take care of safeguarding your key for you," it sounds like you're just doing them a favor.

It would be more honest to say, "I can hold on to a copy of your key and automatically unlock your data when we think you need it opened," but that would make it too obvious that they might do so without your permission.