They are awesome. I'm not sure how they became a fad. But I've owned them for almost 20 years.
The first time you use one, it is a truly unique experience. You don't realize the amount of muscles that are active when relaxing in bed, but when you put on the blanket it lets you feel them..and relax by actively consciously relaxing. Also, anxiety. Wow...
I think it like brings be back to somthing comfortable when I was young? I remember the feeling from being a toddler or something it's an almost nostalgic comfort.
These have been around forever, especially for children with anxiety issues and autism too.
If your having trouble sleeping melatonin is a good start and helps jump-start your circadian rhythm.