So your answer is basically a tautology: you should buy a product because in that way you are getting the ability to sell it. No shit, Sherlock. I didn't know that. lol
But yet, it's the only product that can be cut into millions of pieces with a click, transferred from one part of the planet to the other in seconds, be easily verified, resistant to censorship and completely durable. So, I assume that if lots of people think same like I do, that it does look like a currency, then I see no reason on not using it likewise. Call it belief.
What's so bad if we want to deal with it?
But the agreement is obviously voluntary. People are not liable to return you the things you can live off of once you bought bitcoin. That's the whole point.
Good, that's a feature. It's a feature of free market. You still deny that you don't know your future purchasing power whether there are collaterals or not. You've only focused that, on paper, you'll own an amount.