This kind of scam has been going around for years. Usually the email that is received contains a user's real username and password for a service like their email, cloud storage, or social media, that has simply been pulled from one of the many database leaks or hacks that have been happening for years. The idea is that the naive user sees their own password and panics, believing the rest of the email to be true, when it obviously isn't.
Hey, if you are too stupid to cover your webcam when you are surfing porn and if you have to do that in secret, then you deserve to be a victim of this scam.
I have no idea why people don't have their webcams covered 24/7, unless they are actively making a video call or similar. We know the NSA (and who knows who else) can take photos and record video from webcams without you knowing about it. Go in to your phone or tablet's permission and be shocked at just how many different apps have full control of your camera for no discernible reason. The first thing I did when I got my new laptop, before I even turned it on, was to open it up and physically remove the webcam. If you don't want to do that, put tape over it, like
everyone who works at the FBI does. Buy a case for your phone with a sliding camera cover or similar. Assume all your cameras on all your devices are recording all the time, because they could well be.