Because it's not installed, and they don't want to and shouldn't have to learn something new when there's something not new already at hand which suffices.
If you ever find yourself saying something like, "people can just do X" and wondering why they don't, turn it around and ask yourself, "why can't I just do Y?" In this case, that would be, "Why can't I just make my notebooks work in the viewers that everyone already has agreed upon using (i.e. the WHATWG/W3C hypertext system, i.e. the web browser) instead of asking them to futz around with installing and learning Jupyter?". When you start making excuses for why not, it's the moment you should be able understand another person's reasons for why not Jupyter.
Because it's not installed, and they don't want to and shouldn't have to learn something new when there's something not new already at hand which suffices.
If you ever find yourself saying something like, "people can just do X" and wondering why they don't, turn it around and ask yourself, "why can't I just do Y?" In this case, that would be, "Why can't I just make my notebooks work in the viewers that everyone already has agreed upon using (i.e. the WHATWG/W3C hypertext system, i.e. the web browser) instead of asking them to futz around with installing and learning Jupyter?". When you start making excuses for why not, it's the moment you should be able understand another person's reasons for why not Jupyter.