Why can't coin blockchain protocols all run on nothing but pruned nodes? Say a protocol requires all nodes to prune everything before the most recent 10,000 blocks. If you can verify via the code that the way it's pruning is creating the correct ending balances in all of the addresses, then what is the negative consequence of having no archival history? We're all able to reconcile our own addresses in real time for accounting purposes and can thereby verify that it matches what the protocol says our address has.
I'm aware that this is an extremely fundamental concept of how crypto currency works, but I need help understanding it, because as stated in the title, I am retarded.
and don't fixate on the arbitrary 10,000....... maybe it's 100,000 or maybe it's 1,000,000...... the point is that all nodes would be pruned at N blocks, where N would be high enough to make a hash-rewrite unfeasible.... but at the same time the fact that it is regularly pruned would prevent the situation of a blockchain growing indefinitely forever.
I know there is a reason this can't work (otherwise in undoubtedly would've happened already), I just want to understand what the reason is.