To be honest, I never seen a quilt in my life... no one uses it in Israel.
Is it even comfortable? What's its advantages?
In a sleeping bag, the insulation underneath you is compressed and doesn't add to your warmth. A quilt eliminates that insulation so you get the same warmth with less weight. Since it is more open, it is easier to stick body parts out to regulate your temperature. I also find them less constraining and not as claustrophobic as sleeping bags. Some people have concerns about drafts in the open back of the quilt. I haven't found it a problem down to 25°F. The quilts like EE's are designed to wrap around you and you can also use the included straps to attach (and seal) them to your mattress. IMO they end up the same as a sleeping bag, but you don't carry the insulation you don't use.
Also, I have interacted (on the internet) with at least one person in Israel who uses a quilt. They are their, but they are still new. REI (major outdoor retailer in the US) recently started selling them.