I was told that in rider circles, these protective devices are more politely called "Engine Guards". "We don't use the C word", was what was said. Whatever you call them, I think that this accessory is quite desirable, and I generally install one on any commuter or general purpose machine that I ride.
These accessories are very popular in India, where they are often adorned with rope wrappings and take various forms, some quite complex.
I found this article listing the popular types:
https://rideofy.com/blog/royal-enfield-crash-guard-online/Also, this U-Tube video:
https://www.youtube.com/watch?v=GPfJuzWmjCgThe "Airfly" type is the most ostentatious. I recall reading an Indian RE forum, wherein a member was suggesting that this type is actually dangerous to the rider. He told a story about how a friend had been in an accident with a vehicle, and the bar had bent back around the bike and trapped the riders leg to the side of his bike.
The type I put on my bike isn't on the list of those popular in India, but was readily available for around $80 or less on Ebay. I'd call it "trapezoidal" in shape. It does a great job of protecting the bike and rider. You can see in the attached image, the scar that bears witness to it performing perfectly when I went down on a patch of ice about this time last year. As with many India sourced items, the mounting hardware wasn't quite right, and a bit of home engineering was involved to properly mount the guard so as to not interfere with the 02 sensor. I blend my own "squint eye matching" khaki paint using various shades of Rustoleum from my collection of primary colors, plus white and black.
Royal Enfield military motorcycles seem to have yet another style of guard, that is something of a cross between the "Butterfly" and the "trapezoid" style.