There are billions alive on this planet today. I think it's important to keep both the present and future in mind.
Your second sentence showcases some wildly negative biases. I suspect we could probably save money by improving the efficiency of our social programs and end up with even more to spend on scientific advancement.
I agree that there are many better ways to organize social programs, e.g. replace all of them with negative tax, when some percentage of all tax collected past year is divided equally between all citizens of any age.
Sure well organized society is very impressive, e.g. invention of capitalism and private ownership is the greatest invention ever made, but the point i was trying to make is that it is only a foundation for really exciting stuff like science spaceships, immortality.