Bitcoin is money. Money is math. Math can be measured and quantified objectively. A trustless system is of the highest importance with a decentralized store of value. Proof of work/Consensus/Incentives are perfect for sound money.

Nostr is identities and connections. Social connections are not math. They cannot be measured or quantified objectively. The fundamental principle of a social dynamic is one that revolves around trust.

These are not the same.

Proof of work in bitcoin functions due to the dynamics between blocks, network consensus and incentives: IE the advent of blockchain.

PoW on nostr is just an arbitrary number to meet a relay's requirements. If a spammer has profit incentive, they simply scale their difficulty accordingly. Someone with an incentive will always be willing to pay a higher price (PoW) than a casual user. The obvious outcome here is an ever increasing difficulty that makes nostr unusable for the average user.