Because I don't know what the solution is but I do know that the alternative is going to be no fun at all. One possibility is that we all end up agreeing that we should at least try to reduce our numbers. My parents brought me up with 'replacement' numbers so that we'd end up with a steady population. I'm not so sure if that was wise. And I'm aware that there are many predictions out there that our numbers will eventually top out (they will, either because we do it ourselves, voluntarily or because our resources will run out, an exponentially expanding population in a fixed environment always ends in collapse).
But unless we manage to massively reduce our impact on the environment I don't see a way for the increased consumption and eventual survival of our societies as we know them today. In another comment someone offhandedly asked whether we should all want leisure yachts or not. The obvious answer to that is 'no'. But we probably also shouldn't all want vehicles and the ability to transport ourselves to the end of the world on a whim. Hard choices are ahead of us, the time for easy answers is long behind us.