Permissionless blockchain systems, such as Bitcoin, rely on users using their computational power to solve a puzzle in order to achieve a consensus. To incentivize users in maintaining the system, newly minted coins are assigned to the user who solves this puzzle.
On the other hand, proof of stake systems incentivize coin hoarding as players maximize their utility by holding their stakes. As a result, existing cryptocurrencies do not mimic the day-to-day usability of a fiat currency, but are rather regarded as crypto-assets or investment vectors.
I also think that it's possible to
implement an auction without requiring a semi-trusted party, where every miner in the network is a potential bidder.
