it kind of doesn't matter why it is, it just is (the why might also be unknowable, or too facilely reducible to just-so stories). And it's actually not TOTALLY

it kind of doesn't matter why it is, it just is (the why might also be unknowable, or too facilely reducible to just-so stories). And it's actually not TOTALLY unusual in coronaviruses, it's unusual in the coronavirus subfamily that COVID-19 comes from. There is this very hilarious paper where they talk about this, but also rejigger the phylogenetic trees without describing how they pick what to put in and hide from the trees, e.g. they overload "trivially similar" sequences that happen to have furin cleavage sites, and then there are diagrams where they omit entire huge families of coronaviruses that don't contain the furin cleavage site to "lie to you with pictures" that the furin cleavage site is more common than it actually is. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7836551/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7836551/