>"given the rarity of bitcoin, why wouldn't people value it?" Because rarity in and of itself doesn't confer value. Or every altcoin would be valuable.

>Our economy is built on confidence. Yes, but not only that. Use of fiat currency is made legally compulsory.

Maybe Bitcoin-demanding ransomware plays a useful role in the BTC economy, as it gives people a negative/fear-based reason to obtain BTC.