Because we have no clue of how to, yet.
But I agree that we could throw more people and resources at the problem, if aging didn't seem just natural and the idea of a defeating it didn't seem a bit crazy. But it's also true that the knowledge, tools and methods that might make it possible are only very recent acquisitions.
I can't imagine having this mentality
Of course aging is something we will solve - probably within the next 1000 years.
We will look back on these times like before humans wore clothes and had language.
I'm imagining you as the son of an Egyptian Pharaoh telling this to his dad.
"Really, skip the embalming! If we get you on ice, then they'll be able to revive you by at least 1200 BCE!"