[hnuser123456]

My #1 reason is that once someone figures out how to build large, reliable quantum computers and program them in a practical way and quickly break sha256, bitcoin might be how we find out. That still seems to be a ways away though, and in the meantime, having a mostly-unbreakable digital ledger seems to be valuable.

[Darkstryder]

AFAIK a practical quantum computer would not enable any practical attack against SHA256.

[eitland]

My main reason is because if BTC became mainstream a bunch of crypto nerds would become richer than many banks.

No way they'll allow that to happen I think.

There's of course also

- deflation meaning anyone who believes in Bitcoin and uses one to buy something is either desperate or a fool

- as well as practical issues like energy consumption