One of the basic problems with asking a question like the OP does, is that it assumes a "data or story collection point" like this forum, is somehow the center of the bigfoot universe, and therefore if ANYTHING related to bigfoot has ever happened anywhere, anytime, we'd certainly know about it. THAT just isn't reality. Even in this day and age of connectivity, the real number of people truly involved in "bigfooting" is probably so disproportionate to the number of people who spend time in the woods in North America, or who have EVER had a BF related incident, that it isn't representational of reality. There are MANY people out there involved in research who do NOT actively use the internet or forums like this to do what they do. And there are (rationally guessing) far more people who HAVE had encounters or sightings over the years that will never reveal that to anyone, that again, the numbers are skewed toward 'non-reporting' of encounters.
I'm in my 50's and have read up on the phenomenon since I was a kid in school and didn't become "active" until 2003 when a family member had 2 encounters, but my lifespan barely means anything in relation to how long ago Europeans came to N.A. and how much could or may really have happened in centuries of history that we'll never know about. So to reach for conclusions about populations, and why more haven't been shot, can be entertaining, but we simply don't know what we simply don't know.
Speculation is fun, but absent of real hardcore data, doesn't usually lead you to real substantive answers. It just usually leads to more questions with more speculation, and then it goes down a spiraling vortex till you burn yourself out thinking the lack of an answer means none of it can possibly be true. Then people usually burn out and give up because it's human nature. So, "Blessed are those who HAVE seen... because they can't go back to not believing."
The number that have been shot and killed will probably (in the end) be much higher than you or I would have guessed, because some secrets are best left buried. Time will tell.