I have the same reaction when someone says they only want to live ~80 years. What a terrible outcome when the universe is so massive. There's so much to see, do, try, experience and learn.
There are trillions of galaxies out there and every one of them is different. I could easily happily fill thousands of years just in our solar system.
I'd like to live long enough to explore other solar systems and galaxies and yet the earth by itself is far too large to ever meaningfully explore in a few lifetimes, much less one.
I simply want to see what all is out there. Now, granted, plenty of people consider that a very selfish desire (based on a scarce resources premise) and I'll openly admit to that. It's about as selfish a desire as there can be. I'm ok with that, it's also not a desire that can be actual (not in my lifetime anyway). As such it's equivalent to wanting to be able to fly around like Superman. My desire to learn and experience more will never halt, as such my desire to live an extremely long time will never cease.