It isn't, actually. Bare with me.
I can't even begin to count how many people, aware of this hobby, have started talking about theme parks or specific rollercoasters with me, and when I bring up my favourites (Balder/Helix) and try and explain them, it's always the same responses.
"IT'S MADE OF WOOD?!" "THAT DOESN'T SOUND SAFE" "HOW DO YOU NOT FALL OUT" "YOU WOULDN'T CATCH ME ON THAT" "NOPE, LOOK AT WHAT HAPPENED ON THAT RIDE THAT CRASHED".
Now, negating the latter (although it has had a marked effect, it's a lot of people's go-to when they question safety and call me mental for travelling to go to theme parks), it's been a common theme for a while that an awful lot of the general public have safety concerns about rollercoasters; for many that's part of the thrill of riding them. But for an awful lot of people it is enough to put them off trying it, or visiting in general. Smiler has re-inforced an awful lot of assumptions and pre-conceived beliefs about safety. Alton are going to suffer I feel as they've gone the wrong way in trying to market an already-deemed-unsafe ride type in a park whose recent safety record is an issue for the general public a terrifying experience based around fire.
Where BPB may succeed in changing people's views is by not even acknowledging the open restraints as a selling point, rather, let them come and ride it, love it and realise it's not all bad.