Blame Microsoft!...
For the last 19 years (and billions of documents) MS Word (version 2007 & later) has auto styled & auto corrected the em-dash into its prominence.
MS Word will auto replace a dash into an em-dash when you precede the dash with a space then follow it with a space, a punctuation-less word, & a another space.
Because so many Word users either have mindlessly accepted this 'styling' feature or have wholeheartedly accepted this as styling gospel... A.I. has been, truly, mindlessly misguided in its training.
Which gets back to the moral of the story - 'Garbage In - Garbage Out'!
'nuff said
~Ciao