See, that’s the issue that PDF serves due to its ubiquity. You say “environments” like my mother can pull up a markdown version of a recipe and print it out. Tons of stuff gets sent to people who have no idea what markdown is or how to open it in an appropriate reader. Windows, for example, doesn’t know how to open a .md file, even if the recipient could figure out why they got a zip file with a bunch of randomly (or specifically) labeled parts. Edge will render a PDF in a default windows installation and Safari will do the same in a default OSX install (IIRC); no zips, no extra files, all neatly packed into one.
It’s usually not ideal for communication between people with experience in whatever field is being discussed. I’d rather get a plan in DWG format if it’s a building design, or in Word if it’s a written document I’ll need to edit or reformat. With the exception of an exclusively-text document like an ebook that I’d like to re-flow to a myriad of devices, PDF is the digital form which is the most universal for anything I would previously have requested in dead tree format.