TT bike racing v Formula 1 (yes, I know they are incomparable but allow me a little licence here).
The changes over the years to make F1 racing far safer has worked, thank God. There used to be such horrific crashes with life changing/threatening injuries. It is a great testament to designers and engineers whose skills have saved many a life, I am sure. Many of the race tracks are safer now for the thousands of spectators on site. The cars react differently when in a crash so we rarely see any driver trapped in a car as it bursts into flames.
TT bikes are not affording the same protection for the riders - just the same for non-TT bikes, of course. The Isle of Man seems to be the pinnacle of experience for many bikers and the roads, bends and dips are fraught with danger. All in the "need for speed".
https://thesportsgrail.com/isle-of-man-tt-top-25-fastest-lap-and-top-speed-record-list/
"The Isle of Man TT, also known as the Tourist Trophy races, is a yearly motorcycle racing event held just on Isle of Man in May/June for many years since its establishment in 1907. Many participants have perished in the race, making it one of the most deadly racing events in the world."
I cannot understand why anyone would risk their life in such a pursuit of sport on roads that are not designed for such incredibly high speeds. But there you go - there is no accounting for a lot of things in our crazy world. However, I do feel incredibly sad for families that are bereaved in this sport. I also feel for the ordinary motor bikers who drive on our roads and do so safely and legally yet are branded as thrill-seeking, speed-breaking, dangerous riders.
In short, sandy, one cannot stop someone from risking their life (and possibly others' lives) in the name of sport, but I wish that were not the case.
I have never seen the other course to which you refer so cannot really comment but I assume it has the same sort of inherent dangers.
btw, I am surprised your thread has not attracted more attention...