[s73v3r_]

Why? Killing them requires, well, doing something. You have to actually kill them, which takes effort, and then you have to dispose of the carcasses, which takes effort. On the other hand, simply turning them loose is no effort at all.

[djrogers]

If you own a machete (or rampiri, or kukri), the marginal cost (and frankly effort) of killing a cobra is basically zero. And disposing of the dead ones has to be as easy or easier than disposing of live ones if you factor in any factors related to other people...