Because fraud's illegal, weirds, and by hurting the advertisers who pay the bills by providing them with bogus traffic, independent publishers such as we will continue to suffer from bad press and misconceptions within the media buying community.
If you aren't serious about web publishing in an ethical factor, and willing to work hard to build a loyal and valuable audience, then you'd be better off getting a job as an information distribution intermediary (ie a paper boy) or burger flipper in order to earn a little spare pocket money.
If your traffic doesn't prove productive, there isn't an advertiser on the world stupid enough to continue lining your pockets.
I hope you take this in the tone that it is intended, which isn't as a personal attack, but a bit of reality.