The history of transactions has no importance to the value currency. A dollar that was stolen is just as valuable as any other because they are bearer bonds (like most currencies).
The whole Immutable thing is just translating the concept of a bearer bond to digital space, nothing to do with its intrinsic value.
People are willing to trade their labour and opportunity cost for entries on this ledger.
This is false. Ethereum has higher block rewards (in $) for over a year now. Bitcoin is the second biggest PoW network by mining expenditure.
Ethereum ($38,451,803.7)
Bitcoin ($34,875,489.84)
Before EIP 1559 fees were much more important. Ethereum has higher rewards since about Q3 2020
edit: even worse, f2pool just multiplies the base reward (2 eth) - ignoring uncle rewards and fees, by the wrong number of blocks (based on 15 sec block time - it's actually 13.2s). Trash calculation.
This is, however, true regardless. The value of cryptocurrencies are measured in USD, and it is expectations of this future valuation that backs up the current price.
The only way to make it more certain than expectations, would be by some sort of government decree.
If your implication is that the only thing backing crypto currencies is an expectation of reciprocation then you are mistaken. The qualities you want to hand waive away, and most importantly (though often trivialized), is the inability to roll back the chain which is a function of "consensus power." Consensus power simply quantifies the cost of rolling back x blocks. Bitcoin currently has the highest cost to roll back blocks and therefore the most assurance.