Only 2 people died of rattlesnake bites in 2018, in South Dakaota and Oklahoma.
https://en.wikipedia.org/wiki/List_of_fatal_snake_bites_in_the_United_States
Having said that, I was walking in Arizona once at sundown and heard a rattler in a nearby bush. Scared the devil out of me!!
When I was a kid, my father had a friend who was active in the annual rattlesnake roundup. (An insane few days where the locals go out and, well, round up every rattler they can find.) The bed of his pickup truck had been modified - plywood panels put up around the sides. And they put all the snakes in there. A pickup truck full of angry rattlers. This was insane, on every possible level.
So, one year, he was leaning on one of the boards, for some reason. It gave way. They were not able to count the number of bites he had. The poor man lived, yes. Only because he was 10 minutes from a regional center that had stocked up on antivenin, knowing the roundup was happening. He swelled like a balloon - the flesh on his arms and legs went various colors and literally split - and he was in ICU for months.
Five years later, he was back doing the roundup again. Oy. Men.
https://www.mysanantonio.com/news/local/article/Sweetwater-Rattlesnake-Roundup-kinda-like-a-12746522.php#item-85307-tbla-15My theory is that they were helping a new type of more dangerous rattlesnake to evolve. The ones that didn't rattle, didn't get caught. So the non-rattlers were left to breed more non-rattlers. My theory anyway.
As to them being aggressive. It depends on the variety, and the time of year/temperature. There are some that are mean little bastards, and very aggressive in some circumstances. Not all of them rattle before they strike, too. Most varieties just try to get away, I believe.
I have always heard that Southern Pacific rattlers were particularly nasty. Ran into one adult, who didn't like the cold water from the garden hose (jeez, it was a big snake!) and a couple of babies who periodically managed to squeeze through the 1/4 builder's fabric fence I had around my raised bed. (It was freakish - they dislocated their jaws to do it.) I have a photo somewhere that I'll post if I can find it. The babies are as lethal as the adults. And you will almost assuredly die if you do not get treatment for a rattlesnake bite.