These discussions can get a bit long, so I'll attempt (and fail) to keep it brief.
> Science doesn't really tell us what happens to your consciousness after death.
Currently it doesn't really tell us that there's a consciousness of any sort afterwards. The concept of an afterlife might as well be a coping mechanism and the burden of proof should lie on those in favor of those claims. Maybe some day we'll have an answer. Until then, it's best to stick to what we know. What we know is that one's physical body shapes their mind or at least its expression a great deal, like the case of Phineas Gage and others. Similarly, even the casual descriptions of going under for surgery convey a sense of "lost time", just nothingness.
If I have some sort of a "soul" then it will become more relevant once I'm dead. Until then, it makes sense to look after my body in whatever ways are possible, which includes things like eating well, getting enough sleep, not acting reckless or engaging in risk-taking behavior, limiting intake of harmful substances and so on. It also might include preserving my body around the time of death in case my brain activity can be restored later.
> As to selfishness, why spend the $100k+ on having your body frozen rather than passing that along to your descendants?
I will have no descendants. This is not a world where I'd want any, or worse yet, pursue parenthood due to selfish motivations or societal pressures. It's challenging to do it right and it is not for everyone. Props to the good parents out there, shame on the bad ones, or those who are not ready or qualified to be parents, yet choose that anyways.
> Do you believe that there's something special about you and/or inadequate about other people that makes your greed over a chance at a few more years of life worth the money and time you are taking from them? Why is life about what will "do me much good"? Is that all you think your life is worth? It's just about accruing a bunch of stuff so that you can hopefully spend it on becoming immortal before your clock runs out?
Nothing special at all, just self preservation - I experience life from my own perspective. I would like a continuation of that, within my means. I'm not stealing the last bite of food out of some descendant's mouth, merely using my own capital as I please, after the corresponding taxes have been paid and other investments made, charity donations done and so on. That doesn't seem like an unreasonable thing to do, given how we typically get capital for our contributions to society in one way or another (hopefully that's the case).
We don't tell people that they shouldn't buy nice clothes or cars for themselves because their future descendants could use the resources better, even knowing that those clothes will tatter and those cars will turn into heaps of rust. We don't tell people that they shouldn't buy medicine or medical procedures that might improve their health just because of them being a certain age, or more bluntly, we don't tell them that they should die so that the state and their descendants can take whatever inheritance there is.
> Usually, they are also part of some weird cult, too, that convinces them that they can beat the odds.
I think it probably boils down to simple maths: 0.01% is still better than 0%. Probably depends on how much you want to live. On the flip side, there are also those who say that a lifetime is more than enough and they're happy to have an end to a life well lived.
> Death is ultimately a natural part of life, and I guess the unknown part of it is so terrifying that we spend so much of life futilely trying to prevent it.
Unfortunately, infant mortality was also a natural part of life, until we took an effort to improve things. There's no reason why death or even deterioration at a late age couldn't be engineering problems to be solved. A world without Alzheimer's or cancer would be a better world, even if both of those are also natural. Imagine if you could preserve someone terminally ill or someone in need of an unavailable organ donation, until later.
> I think it's a lot better to embrace the fact that you get about 100 years on this rock to advance the state of the world as much as you can before passing the job of being its steward onto the next generation.
There is no reason why someone couldn't live with this assumption (regardless of whether they choose to have kids or not), while hoping for or investing in healthcare advancements, or even set aside some money for cryonics if they want, instead of buying more real estate or whatever. All in all, I don't expect to change any opinions, because mine is as alien to you as yours is to me. I don't appreciate that some of it reads condescending and so accusatory, though.