> as of now, Bitcoin hasn't been hacked

We should be cautious about whether past precedent applies to future bitcoin, because the bitcoin halving mechanism ensures that bitcoin enters uncharted territory (with regards to the incentives at play) every four years for the next ~100.

Satoshi's design was that bitcoin would be used as cash and transaction volume would provide the funds to secure the network. That largely hasn't happened (it's a "store of value" now, lightning exists, etc.), so mining incentives are still ~95-98% funded from the exponentially diminishing supply of new coins.

Short of some institution stepping in to secure the bitcoin network by mining at a loss, it's hard not to imagine a 51% attack being relatively cheap on the time scale of decades.