We call it a 51% attack an attack, but from the perspective of PoW it's always about the chain with the most work. Anyone is just as valid as anyone else to pro

We call it a 51% attack an attack, but from the perspective of PoW it's always about the chain with the most work. Anyone is just as valid as anyone else to propose blocks. That's the point of Bitcoin: a way to always figure what the truth is, and make it as expensive as possible for people to attack/change this truth. The only problem here is that PoW only knows one cost: hashing, and due to macro shifts in mining hardware this can sometimes go down a lot more than the value of a coin (which makes the cost of this attack worth it). As soon as you start introducing measures to subvert this attack you are subverting either decentralization or stability. If you for example program clients to not accept reorgs deeper than 10 blocks (for example) you simply introduce new attack vectors that can split the network (into following different chains - which is even scarier than 51% attacks). If every x blocks you snapshot the chain and force everyone to follow that snapshot you just centralized the chain, etc.