It's been a while since I've set up a windows machine and this may already be mentioned, but when I sign up for signal I got lots of warnings that were like "warning if you lose your phone and encryption key you will lose your data"

That way I know what I'm signing up for.

Just put "encrypt? Yes no" in the on-boarding flow and let people know what the risks are and what they may be protecting against. I'd probably default to off because people don't read wizards and the last thing someone wants is to lose their entire HDD because they accidentally made a decision they didn't understand.

And maybe for a certain period of time they can nudge users to read about encryption and decide if it's right for them, or just easily disable that nudge. Maybe even basic education like "if you find yourself forgetting your password often then maybe encryption is not for you" or something like that.

Windows is already optimized for extracting as much value from customers as possible, may as well help them make at least one informed decision.