I am one of those hard money people. The work secures the network. In order to alter the ledger, you need to reverse not just one block, but every block after i

I am one of those hard money people. The work secures the network. In order to alter the ledger, you need to reverse not just one block, but every block after it, means you would have to redo the work for every single block. All the while, the rest of the network keep working along the real chain, mining new blocks. The work makes it impossible to alter the chain.