I would say it's more fair to ask "why does the Western world consume so many resources?". I think the answer to that is based on how we define success as well as our sense of entitlement. Let's face it, success means money, cars, big houses, lots of trendy clothes and other wasteful things. How we got to considering success as these things, I don't know, but we're certainly going to need to redefine success if this planet is going to succeed.
The second cause is probably our sense of entitlement. Once again, I'm not sure where this came from. For some reason though we feel that turning 16 means we "deserve" to have a car. We feel that Getting a job means we "deserve" to have a big screen TV. Try to tell people that what they "deserve" is hurting the world so they shouldn't get it and they will fight you to the bitter end. The truth is though, we don't "deserve" anything. There is no universal right to cars or big screen TVs. Heck, over history people have worked themselves to the bone just to buy food, but for us mechanization combined with cheap oil makes us feel like we should have those things, even if we don't even know what true hard work is.
Those that push the blame for ecological crises to China and India are hypocrites. Yes, they are coming up in the world and in doing so are consuming resources. However, they're doing so because they aspire to the "glamorous" life that WE display. Also, just because they're using resources doesn't mean we aren't. Stop worrying about fixing other countries and try fixing your own. Maybe they'll aspire to our new, greener, lifestyle.