Because to do so would require the institution of global socialism or communism--and we know what great stewards of the environment THEY are. In any event, a rule-everything tyrrany. Examples: they want to outlaw backyard barbecues because of the soot and CO2, and also gas-powered lawnmowers. Every, repeat, every aspect of your life would be controlled. Me, I'll take the heat and leave the anti-human "pro nature" crowd for you.
Don't forget they'll want to go diaperless, too. It's natural, you know.
Diaperless Babies Seen As Earth-Friendly Solution