I think it happened because computers got more internally complex as their UIs got simpler, and thus the people who wouldn't immediately gravitate towards hacking had far less incentive to try it and see if they liked it. You pretty much
had to know at least some BASIC to do things on an '80s home computer - today you can generally operate a computer without even being able to
read. It's a sad but probably inevitable consequence of the drive to bring computers to mass use in the '80s and '90s.
Fortunately, some of us still care, and while it's sad that we don't have so many people to share our experiences and passions with as we used to, the machines are still here and, for the most part, still working

Nothing is truly dead if even one person still cherishes it.