Because I care to what happens about all living humans today. I simply don't care about the long term survival of our species.
Spreading across the galaxy or the universe so that there can be more humans alive or to ensure that if one planet gets wiped out, some humans live on are placing value on the existence of humans as a species in the universe. That's what I don't care about. I don't think we have intrinsic value that needs to be preserved.
It's hard to pinpoint an exact generation where I stop caring. Here's how I like to think of it.
If every human alive today died instantly and painlessly, ending the human species and potentially eliminating all sentient life in the universe, I wouldn't care. The people felt no pain, experienced no dread.
The only reason to care in that instance is if you believe that the human race has inherent value just be being alive. That's what I don't have.
Now, the interaction of this philosophy and the real world isn't always clean but in general, it leads me to prioritize current human life over future human life especially over the long term.
So, for example, a dollar spent feeding a hungry child today takes precedence over a dollar spent exploring the universe even if that exploration lays the groundwork for humans being a multi planetary species 500 years from now.
It's a strange position. There will always be hungry children until we fundamentally change human nature.
I'd argue we're more likely to change human nature through space colonization than here on Earth, but that's a debate I don't expect to see much value from.
<i>> I care to what happens about all living humans today. I simply don't care about the long term survival of our species.</i>
<i>> why should I care whether all of our eggs are in one basket, or two baskets, or a million baskets? The survival of the human race as a whole is not a concern of mine.</i>
In short, because others care.
You cannot reach your goals alone. You need a cooperation from others. But if you didn't care what they care, there would be no cooperation, or cooperation would be not so good as it might be.
Cooperation needs shared values, and the more values are shared, the more effective cooperation would be. If you care only about your goals and not about goals of others, than others would not play with you. If you share some goals (I believe that those who care about long term benefits value short term also) then they accept your cooperation when working on short term goals, but you will not have any influence over them, when they work on long term goals. The only lever on them you would have is a force. Military, political, financial or any other. They would not cooperate willingly.
You can choose war and force those who have other values to work on your values. Or you can respect their values and cooperate with others on them. It is your choice.
