> how many times in history a continental network partition of the internet has happened?
Continental? No. Country-wide? Many, many times.
Imagine being in Egypt during the Arab Spring revolution when the government shut off Internet access. Imagine selling product to people for Bitcoin, seeing your client software accept the transaction because "enough time has passed", and then a few days/weeks later, when Internet access is restored, seeing your wallet balance get clobbered by the much-longer global chain.
/shudder