As the last paragraph of the OP points out, the majority of experiences are positive and, to circle back around to the first paragraph, bad trips have historically been blown out of proportion.
This propaganda around bad trips, and there was a lot of propaganda coming from the Nixon administration, primes people’s experiences. Rick Doblin, founder of MAPS, talks about priming (or expectations) as a major and often glossed over aspect of mindset (set and setting).
My point, expectations of bad trips help create them as much as past trauma etc. And, we had a president who had such a hard on for hippies we’re still putting people in prison for growing mushrooms.
So, Nixon is still creating bad trips. Not only through the propaganda mentioned above. But also the terror of going to prison, which is a terrible thing to take into the psychedelic headspace.