You are equating the reliability of a server machine with the reliability of a user's client machine, when in reality these are not remotely similar. Laptops ar

You are equating the reliability of a server machine with the reliability of a user's client machine, when in reality these are not remotely similar. Laptops are regularly suspended and move between networks, losing connectivity. Phones even more so. Consumer internet is unreliable, usually with poor outgoing bandwidth. Mobile networks even more so. Etc. When I share a document with five coworkers then close my laptop, the others need to be able to keep working. Under your model, that means they'd need to choose a new server. Guess what? This means you now need a consensus protocol. One where partitions happen 1000x more often, it is regularly necessary to operate without a quorum, latency is high and totally unpredictable, and all kinds of other properties that make the problem exponentially harder.