Isn't that because it's sometimes useful to kill everything?
I'm no expert, but my understanding of the problem is that if you attempt to kill everything, you'll end up with a few super-resistant [things] (organisms, bacteria etc.) who'll only increase the problem:
Going off on a slight tangent, my personal worry is where we'll be after another 10 years of antibac hand wash use. I'm open to being corrected, but my current understanding is that we should be very, very worried.
I was being pretty imprecise there; the point is that Roundup is (again, imprecisely) potent and broad-spectrum. You couldn't just spray it over a normal crop; it would kill the crop along with the weeds.
I'm no expert, but my understanding of the problem is that if you attempt to kill everything, you'll end up with a few super-resistant [things] (organisms, bacteria etc.) who'll only increase the problem:
http://evoled.dbs.umt.edu/lessons/background.htm
Going off on a slight tangent, my personal worry is where we'll be after another 10 years of antibac hand wash use. I'm open to being corrected, but my current understanding is that we should be very, very worried.