Why is one of the most common default arguments against immortality “we’d just be floating in space suffering forever”?

From where did it originate and why is it so common? Is there anything related to this, or is it just considered bunk to proper philosophers and only exists in the popular zeitgeist and not in more academic settings?

Part of why I ask is that the premise doesn’t make a whole lot of sense to me. If anything definable as you is able to exist indefinitely that implies you have some immunity to entropy and that whatever consciousness interacts with the world is capable of overcoming any resistance implying an infinite energy output that could be used to create a functionally indestructible construct within which you could live. If it’s a body you could just run on a giant hamster wheel and power something forever (maybe hellish for you but could be a net good for a large number of people you’d sustain). If just an individual neuron survives as “technically you being alive” arguably even better. And if you just don’t age then you would die in space in a matter of minutes.

I’m curious what the thoughts of people who are better at this than I am think.