I get this argument if it was for e.g. gold. A physical asset, thousands of years of people appreciating it, nothing else like it. But why might it be rational

I get this argument if it was for e.g. gold. A physical asset, thousands of years of people appreciating it, nothing else like it. But why might it be rational to put some of your net worth to bitcoin? What speaks for bitcoin existing in a meaningful form 50 years from now, instead of some improved, different (blockchain-based or not) digital asset?