Because they are generally not a threat. Certainly they are a manageable one with even a modicum of effort.
Sorry to say, but your postings in this thread suggest that you can never forgive a snake for taking your pet and now every snake is a "threat."
Snakes can be threats, but not just be virtue of being a snake.
What's the difference between an armed thug invading my home and and hunter in the woods? Both are armed and are equally "threats" so I should kill them both dead?
The ability to reason and see nuance is what separates humans from animals.