That’s because they DON’T.
See post above.
Liars gonna lie.
Maybe they don’t get that big where you live. I took one out of Samsula, Florida that was 12 foot long - after the head and rattles were removed. That were 43 years ago. That was common in that area back then. The skin was mounted on a 14’ 12x1 pine plank, also out of Samsula. They used to do a lot of lumbering around there. Lot of timber rattlers in those days. Skin was displayed in an office supply company in Daytona for several years. Gave the rattles to my driver. The head was no account as it was messed up by a shot from a model 24, W-W Silvertip did the trick. I was going home down state road 3 one evening and several hundred yards ahead was what looked like a big black cable across the road. As I approached it, it started the narrow down on the left side of the road. By the time I stopped it had crawled of the right side of the road. Didn’t get to see it up close. The only guess I could make was a Black King Snake. That was on North Merritt aIsland which is a wild life preserve. Had to slow down as I was doing 70 mph on a standard model GL1100 and I was afraid if I hit it it would have torn the front end of my motor. Circa 1986.