Pilot here - it's legal to fly at 12,500 in an unpressurized aircraft indefinitely. See https://www.ecfr.gov/current/title-14/chapter-I/subchapter-F.... Cabin pressurization is set to a lower altitude, but that's not for a legal requirement. It's just nicer to be at higher pressurization.
And, I mean, think about it - there are _towns_ at 9k+ feet.
In what way is the content of your comment strengthened by waving about a PPL? It serves only the patronize. Excise it, what does it change?
Similarly, assuming that most of the audience here, aviation knowledge or not is unaware that there are mountains with people.
Anyway, passenger cabins require 8,000 ft for normal operation, so it's a bit misleading to say there's no legal requirement. https://www.law.cornell.edu/cfr/text/14/25.841. (And yes, I know the difference between airworthiness and operations, still misleading). Also why I'd bet a good sum you're a PPL.
I'm not even in the US; you're barking up the wrong tree. I apologize for disclosing a relevant fact. Won't happen again. Thanks for the link to CFR25.
And, I mean, think about it - there are _towns_ at 9k+ feet.